Problema com o Indy IdHttp Post no Delphi 2010

Estou com um problema com o método Indy IdHttp Post. A função CallRpc () compilada com o Delphi 2007 funciona bem, mas o mesmo código compilado com o Delphi 2010 gera exceção.

O que devo considerar ao mudar o Delphi 2007 Indy TIdHttp para Delphi 2010 Indy TIdHttp?

function CallRpc(const sURL, sXML: string): string;
var
  SendStream : TStream;
  IdHttp     : TIdHttp;
begin
  SendStream := TMemoryStream.Create;
  IdHttp := TIdHttp.Create(nil);
  try
      IdHttp.Request.Accept        := '*/*';
      IdHttp.Request.ContentType   := 'text/sXML';
      IdHttp.Request.Connection    := 'Keep-Alive';
      IdHttp.Request.ContentLength := Length(sXML);

      StringToStream(sXML, SendStream);  
      SendStream.Position := 0;

      Result := IdHttp.Post(sURL, SendStream);
  finally
    IdHttp.Free;
    SendStream.Free;
  end;
end;

Adição 25.1.2009:

A exceção é esta: EIdConnClosedGracfully

A resposta é esta:

<?xml version='1.0' encoding='us-ascii'?>
<!DOCTYPE Error [ <!ELEMENT Error (ErrorMessage,DebuggingInfo*)> <!ATTLIST Error Date CDATA #REQUIRED Time CDATA #REQUIRED> <!ELEMENT ErrorMessage (#PCDATA )>  <!ELEMENT DebuggingInfo (#PCDATA )> ] >
<Error Date='01/25/2010' Time='08:57:12'>
<ErrorMessage>
    XML SERVER ERROR: There was a SYSTEM ERROR error in the Incoming XML Response: $ZE=&lt;UNDEFINED&gt;lexan+196^%eXMLLexAnalyzer
</ErrorMessage>

Solução 26.1.2009:

function CallRpc(const sURL, sXML: string): string; 
var 
  SendStream : TStream; 
  IdHttp     : TIdHttp; 
  sAnsiXML: Ansistring;   // <-- new
begin 
  sAnsiXML := sXML;  // <-- new: Implicit string cast

  SendStream := TMemoryStream.Create; 
  IdHttp := TIdHttp.Create(nil); 
  try 
     IdHttp.Request.Accept        := '*/*'; 
     IdHttp.Request.ContentType   := 'text/sXML'; 
     IdHttp.Request.Connection    := 'Keep-Alive'; 
     IdHttp.Request.ContentLength := Length(sAnsiXML); // <-- new

     SendStream.Write(sAnsiXML[1], Length(sAnsiXML));  // <-- new
     SendStream.Position := 0; 

     Result := IdHttp.Post(sURL, SendStream); 
  finally 
   IdHttp.Free; 
   SendStream.Free; 
  end; 

fim;

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