O carregamento de qualquer página do MVC falha com o erro "Um item com a mesma chave já foi adicionado".

Estou tendo um problema intermitente que está aparecendo em apenas um servidor e está fazendo com que todas as páginas do MVC não sejam carregadas com o erro "Um item com a mesma chave já foi adicionado".

Reiniciar o pool de aplicativos corrige o problema, mas até lá, o carregamento de qualquer página mvc gera a seguinte exceção:

Event code: 3005 
Event message: An unhandled exception has occurred. 
Event time: 10/11/2012 08:09:24 
Event time (UTC): 10/11/2012 08:09:24 
Event ID: d76264aedc4241d4bce9247692510466 
Event sequence: 6407 
Event occurrence: 30 
Event detail code: 0 

Application information: 
    Application domain: /LM/W3SVC/21/ROOT-2-129969647741292058 
    Trust level: Full 
    Application Virtual Path: / 
    Application Path: d:\websites\SiteAndAppPoolName\ 
    Machine name: UKSERVER 

Process information: 
    Process ID: 6156 
    Process name: w3wp.exe 
    Account name: IIS APPPOOL\SiteAndAppPoolName 

Exception information: 
    Exception type: ArgumentException 
    Exception message: An item with the same key has already been added.

Server stack trace: 
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer)
   at System.Web.WebPages.Scope.WebConfigScopeDictionary.<>c__DisplayClass4.<.ctor>b__0()
   at System.Lazy`1.CreateValue()

Exception rethrown at [0]: 
   at System.Lazy`1.get_Value()
   at System.Web.WebPages.Scope.WebConfigScopeDictionary.TryGetValue(Object key, Object& value)
   at System.Web.Mvc.ViewContext.ScopeGet[TValue](IDictionary`2 scope, String name, TValue defaultValue)
   at System.Web.Mvc.ViewContext.ScopeCache.Get(IDictionary`2 scope, HttpContextBase httpContext)
   at System.Web.Mvc.ViewContext.GetClientValidationEnabled(IDictionary`2 scope, HttpContextBase httpContext)
   at System.Web.Mvc.Html.FormExtensions.FormHelper(HtmlHelper htmlHelper, String formAction, FormMethod method, IDictionary`2 htmlAttributes)
   at System.Web.Mvc.Html.FormExtensions.BeginForm(HtmlHelper htmlHelper, String actionName, String controllerName)
   at ASP._Page_Views_Dashboard_Functions_BookingQuickLookup_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Functions\BookingQuickLookup.cshtml:line 3
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData)
   at ASP._Page_Views_Dashboard_Functions_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Functions.cshtml:line 5
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.Html.RenderPartialExtensions.RenderPartial(HtmlHelper htmlHelper, String partialViewName, Object model)
   at ASP._Page_Views_Dashboard_Index_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Index.cshtml:line 9
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
   at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19()
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)
   at System.Web.Mvc.Controller.ExecuteCore()
   at System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext)
   at System.Web.Mvc.MvcHandler.<>c__DisplayClass6.<>c__DisplayClassb.<BeginProcessRequest>b__5()
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass1.<MakeVoidDelegate>b__0()
   at System.Web.Mvc.MvcHandler.<>c__DisplayClasse.<EndProcessRequest>b__d()
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)



Request information: 
    Request URL: http://SiteAndAppPoolName.spawtz.com/Dashboard 
    Request path: /Dashboard 
    User host address: 86.164.135.41 
    User:  
    Is authenticated: False 
    Authentication Type:  
    Thread account name: IIS APPPOOL\SiteAndAppPoolName 

Thread information: 
    Thread ID: 17 
    Thread account name: IIS APPPOOL\SiteAndAppPoolName 
    Is impersonating: False 
    Stack trace:    at System.Lazy`1.get_Value()
   at System.Web.WebPages.Scope.WebConfigScopeDictionary.TryGetValue(Object key, Object& value)
   at System.Web.Mvc.ViewContext.ScopeGet[TValue](IDictionary`2 scope, String name, TValue defaultValue)
   at System.Web.Mvc.ViewContext.ScopeCache.Get(IDictionary`2 scope, HttpContextBase httpContext)
   at System.Web.Mvc.ViewContext.GetClientValidationEnabled(IDictionary`2 scope, HttpContextBase httpContext)
   at System.Web.Mvc.Html.FormExtensions.FormHelper(HtmlHelper htmlHelper, String formAction, FormMethod method, IDictionary`2 htmlAttributes)
   at System.Web.Mvc.Html.FormExtensions.BeginForm(HtmlHelper htmlHelper, String actionName, String controllerName)
   at ASP._Page_Views_Dashboard_Functions_BookingQuickLookup_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Functions\BookingQuickLookup.cshtml:line 3
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData)
   at ASP._Page_Views_Dashboard_Functions_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Functions.cshtml:line 5
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.Html.RenderPartialExtensions.RenderPartial(HtmlHelper htmlHelper, String partialViewName, Object model)
   at ASP._Page_Views_Dashboard_Index_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Index.cshtml:line 9
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
   at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19()
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)
   at System.Web.Mvc.Controller.ExecuteCore()
   at System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext)
   at System.Web.Mvc.MvcHandler.<>c__DisplayClass6.<>c__DisplayClassb.<BeginProcessRequest>b__5()
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass1.<MakeVoidDelegate>b__0()
   at System.Web.Mvc.MvcHandler.<>c__DisplayClasse.<EndProcessRequest>b__d()
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)


Custom event details: 

Como mencionado, é toda ação do MVC que gera esse erro até que o pool de aplicativos seja reiniciado, e o erro parece estar ocorrendo emSystem.Web.WebPages.Scope.WebConfigScopeDictionary.TryGetValue(Object key, Object& value)

Alguém já viu esse problema antes? Isso está acontecendo apenas nesse servidor, em qualquer um dos pools de aplicativos no servidor (não confinado a este) e um reinício do pool de aplicativos o ordena.

Qualquer ajuda muito apreciada.

Felicidades,

Mateus

EDITAR:

Aqui está o arquivo web.config:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
    <section name="listManagers" type="Spawtz.ListManagersConfigSection, SpawtzConfiguration" />
    <sectionGroup name="elmah">
      <section name="security" requirePermission="false" type="Elmah.SecuritySectionHandler, Elmah" />
      <section name="errorLog" requirePermission="false" type="Elmah.ErrorLogSectionHandler, Elmah" />
      <section name="errorMail" requirePermission="false" type="Elmah.ErrorMailSectionHandler, Elmah" />
      <section name="errorFilter" requirePermission="false" type="Elmah.ErrorFilterSectionHandler, Elmah" />
    </sectionGroup>
    <sectionGroup name="system.web.webPages.razor" type="System.Web.WebPages.Razor.Configuration.RazorWebSectionGroup, System.Web.WebPages.Razor, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
      <section name="host" type="System.Web.WebPages.Razor.Configuration.HostSection, System.Web.WebPages.Razor, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" />
      <section name="pages" type="System.Web.WebPages.Razor.Configuration.RazorPagesSection, System.Web.WebPages.Razor, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" />
    </sectionGroup>
  </configSections>
  <appSettings>
    <add key="ConnectionString" value="cs" />
  </appSettings>
  <log4net>
    <appender name="SmtpAppender" type="log4net.Appender.SmtpAppender">
      <to value="[email protected]" />
      <from value="[email protected]" />
      <subject value="Error in SiteAndAppPoolName Spawtz Application" />
      <smtpHost value="127.0.0.1" />
      <bufferSize value="1" />
      <lossy value="true" />
      <evaluator type="log4net.spi.LevelEvaluator">
        <threshold value="WARN" />
      </evaluator>
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="User: %X{User} %n%d [%t] %-5p %c [%x] - %m%n%n%n" />
      </layout>
    </appender>
    <root>
    </root>
    <logger name="Error">
      <level value="ERROR" />
      <appender-ref ref="SmtpAppender" />
    </logger>
  </log4net>
  <system.web>
    <!--  DYNAMIC DEBUG COMPILATION
          Set compilation debug="true" to enable ASPX debugging.  Otherwise, setting this value to
          false will improve runtime performance of this application. 
          Set compilation debug="true" to insert debugging symbols (.pdb information)
          into the compiled page. Because this creates a larger file that executes
          more slowly, you should set this value to true only when debugging and to
          false at all other times. For more information, refer to the documentation about
          debugging ASP.NET files.
    -->
    <compilation defaultLanguage="c#" debug="true" targetFramework="4.0">
      <assemblies>
        <add assembly="System.Web.Abstractions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Web.Helpers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Web.Routing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Web.WebPages, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Data.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
      </assemblies>
    </compilation>
    <!--  CUSTOM ERROR MESSAGES
          Set customErrors mode="On" or "RemoteOnly" to enable custom error messages, "Off" to disable. 
          Add <error> tags for each of the errors you want to handle.

          "On" Always display custom (friendly) messages.
          "Off" Always display detailed ASP.NET error information.
          "RemoteOnly" Display custom (friendly) messages only to users not running 
           on the local Web server. This setting is recommended for security purposes, so 
           that you do not display application detail information to remote clients.
    -->
    <!--<customErrors mode="On" defaultRedirect="Error.aspx" />-->
    <customErrors mode="Off" />
    <!--  AUTHENTICATION 
          This section sets the authentication policies of the application. Possible modes are "Windows", 
          "Forms", "Passport" and "None"

          "None" No authentication is performed. 
          "Windows" IIS performs authentication (Basic, Digest, or Integrated Windows) according to 
           its settings for the application. Anonymous access must be disabled in IIS. 
          "Forms" You provide a custom form (Web page) for users to enter their credentials, and then 
           you authenticate them in your application. A user credential token is stored in a cookie.
          "Passport" Authentication is performed via a centralized authentication service provided
           by Microsoft that offers a single logon and core profile services for member sites.
    -->
    <authentication mode="Forms" />
    <!--  AUTHORIZATION 
          This section sets the authorization policies of the application. You can allow or deny access
          to application resources by user or role. Wildcards: "*" mean everyone, "?" means anonymous 
          (unauthenticated) users.
    -->
    <authorization>
      <allow users="*" />
      <!-- Allow all users -->
      <!--  <allow     users="[comma separated list of users]"
                             roles="[comma separated list of roles]"/>
                  <deny      users="[comma separated list of users]"
                             roles="[comma separated list of roles]"/>
            -->
    </authorization>
    <!--  APPLICATION-LEVEL TRACE LOGGING
          Application-level tracing enables trace log output for every page within an application. 
          Set trace enabled="true" to enable application trace logging.  If pageOutput="true", the
          trace information will be displayed at the bottom of each page.  Otherwise, you can view the 
          application trace log by browsing the "trace.axd" page from your web application
          root. 
    -->
    <trace enabled="false" requestLimit="10" pageOutput="false" traceMode="SortByTime" localOnly="true" />
    <!--  SESSION STATE SETTINGS
          By default ASP.NET uses cookies to identify which requests belong to a particular session. 
          If cookies are not available, a session can be tracked by adding a session identifier to the URL. 
          To disable cookies, set sessionState cookieless="true".
    -->
    <sessionState mode="InProc" stateConnectionString="tcpip=127.0.0.1:42424" sqlConnectionString="data source=127.0.0.1;Trusted_Connection=yes" cookieless="false" timeout="20" />
    <!--  GLOBALIZATION
          This section sets the globalization settings of the application. 
    -->
    <globalization requestEncoding="utf-8" responseEncoding="utf-8" />
    <pages validateRequest="false" controlRenderingCompatibilityVersion="4.0" clientIDMode="AutoID" pageParserFilterType="System.Web.Mvc.ViewTypeParserFilter, System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" pageBaseType="System.Web.Mvc.ViewPage, System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" userControlBaseType="System.Web.Mvc.ViewUserControl, System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
      <namespaces>
        <add namespace="System.Web.Helpers" />
        <add namespace="System.Web.Mvc" />
        <add namespace="System.Web.Mvc.Ajax" />
        <add namespace="System.Web.Mvc.Html" />
        <add namespace="System.Web.Routing" />
        <add namespace="System.Web.WebPages" />
        <add namespace="System.Linq" />
        <add namespace="System.Collections.Generic" />
        <add namespace="SpawtzController.ViewModels" />
        <add namespace="SpawtzController" />
      </namespaces>
      <controls>
        <add assembly="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" namespace="System.Web.Mvc" tagPrefix="mvc" />
      </controls>
    </pages>
    <httpHandlers>
      <add path="*" verb="/Views/*" type="System.Web.HttpNotFoundHandler" />
      <add verb="*" path="*.mvc" validate="false" type="System.Web.Mvc.MvcHttpHandler, System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
      <add path="Telerik.Web.UI.WebResource.axd" verb="*" type="Telerik.Web.UI.WebResource, Telerik.Web.UI" validate="false" />
      <add path="Telerik.Web.UI.DialogHandler.aspx" type="Telerik.Web.UI.DialogHandler" verb="*" validate="false" />
      <add verb="POST,GET,HEAD" path="elmah.axd" type="Elmah.ErrorLogPageFactory, Elmah" />
    </httpHandlers>
    <httpModules>
      <add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah" />
      <add name="ErrorMail" type="Elmah.ErrorMailModule, Elmah" />
      <add name="FixIIS5xWildcardMapping" type="Elmah.FixIIS5xWildcardMappingModule, Elmah" />
    </httpModules>
  </system.web>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="MvcContrib" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-2.0.34.0" newVersion="2.0.34.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Castle.Core" publicKeyToken="407dd0808d44fbdc" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-2.5.1.0" newVersion="2.5.1.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Castle.Windsor" publicKeyToken="407dd0808d44fbdc" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-2.5.1.0" newVersion="2.5.1.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
  <system.web.webPages.razor>
    <host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
    <pages pageBaseType="System.Web.Mvc.WebViewPage">
      <namespaces>
        <add namespace="System.Web.Mvc" />
        <add namespace="System.Web.Mvc.Ajax" />
        <add namespace="System.Web.Mvc.Html" />
        <add namespace="System.Web.Routing" />
      </namespaces>
    </pages>
  </system.web.webPages.razor>
  <connectionStrings>
    <add name="Spawtz" connectionString="cs" />
  </connectionStrings>
  <elmah>
    <errorLog type="Elmah.SqlErrorLog, Elmah" connectionStringName="Spawtz" applicationName="SiteAndAppPoolName" />
    <security allowRemoteAccess="yes" />
    <errorFilter>
      <test>
        <equal binding="HttpStatusCode" value="404" type="Int32" />
      </test>
    </errorFilter>
  </elmah>
  <system.webServer>
    <validation validateIntegratedModeConfiguration="false" />
    <modules runAllManagedModulesForAllRequests="true">
      <remove name="UrlRoutingHandler" />
      <remove name="ErrorLog" />
      <remove name="ErrorMail" />
      <add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah" preCondition="managedHandler" />
      <add name="ErrorMail" type="Elmah.ErrorMailModule, Elmah" preCondition="managedHandler" />
      <add name="ErrorFilter" type="Elmah.ErrorFilterModule, Elmah" />
    </modules>
    <handlers>
      <remove name="UrlRoutingHandler" />
      <remove name="elmah" />
      <remove name="BlockViewHandler" />
      <add name="BlockViewHandler" path="/Views/*" verb="*" preCondition="integratedMode" type="System.Web.HttpNotFoundHandler" />
      <add name="Mvc" path="*" verb="*" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework64\v2.0.50727\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="None" preCondition="classicMode,runtimeVersionv2.0,bitness64" />
      <add name="Telerik_Web_UI_DialogHandler_aspx" verb="*" preCondition="integratedMode" path="Telerik.Web.UI.DialogHandler.aspx" type="Telerik.Web.UI.DialogHandler" />
      <add name="elmah" verb="POST,GET,HEAD" path="elmah.axd" type="Elmah.ErrorLogPageFactory, Elmah" />
      <add name="Telerik_Web_UI_WebResource_axd" path="Telerik.Web.UI.WebResource.axd" verb="*" type="Telerik.Web.UI.WebResource, Telerik.Web.UI" />
    </handlers>
    <defaultDocument>
      <files>
        <remove value="iisstart.htm" />
        <remove value="index.html" />
        <remove value="index.htm" />
        <remove value="Default.asp" />
        <remove value="Default.htm" />
      </files>
    </defaultDocument>
  </system.webServer>
  <location path="elmah.axd">
    <system.web>
      <authorization>
        <allow roles="Administrators" />
        <deny users="?" />
      </authorization>
    </system.web>
  </location>
</configuration>

EDITAR NOVAMENTE:

Ok, já que parece que não há uma resposta fácil para a pergunta acima, talvez haja uma resposta para esta pergunta: Posso de alguma forma configurar o IIS para reciclar automaticamente o pool de aplicativos depois de encontrar um número especificado de erros dentro de um período de tempo especificado? Eu sei que eu poderia ativar a proteção rápida contra falhas, mas não é isso que estou procurando, pois teria de reiniciar manualmente o pool de aplicativos. Como uma solução alternativa (leia-se: hack ...) Eu quero consertá-lo para que ele se reinicia se ele recebe uma carga de erros em uma linha. Isso é factível em vez disso?

Mais uma edição

Ok, este erro ocorreu em outro servidor esta manhã também, então parece que não é apenas a configuração do servidor que está causando isso. Talvez seja algo no meu código, mas estou perplexo sobre como diagnosticar isso, já que não posso replicá-lo e não posso depurar nele ... Parece que tenho mais algumas investigações para fazer.

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