Dependências do Maven não podem ser resolvidas

Estou a usarApache Maven3 e, desde dois ou três dias, algumas dependências não podem mais ser resolvidas, o que primeiro não apresentava problemas. Para ser mais específico, é:

maven-findbgs-plugin:plugin:1.3.1maven-cobertura-plugin:plugin:1.3

Eles não deveriam ser incluídos pelo próprio maven?

Minhaspom.xml Arquivo

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <artifactId>xyz</artifactId>
  <name>xyz</name>
  <description>xyz</description>
  <repositories>
      <repository>  
        <id>prime-repo</id>  
        <name>PrimeFaces Maven Repository</name>  
        <url>http://repository.primefaces.org</url>  
        <layout>default</layout>  
    </repository>  
  </repositories>
  <dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>${springframework-version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.webflow</groupId>
        <artifactId>spring-faces</artifactId>
        <version>${springwebflow-version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-core</artifactId>
        <version>${springsecurity-version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-config</artifactId>
        <version>${springsecurity-version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-web</artifactId>
        <version>${springsecurity-version}</version>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>${org.slf4j-version}</version>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>jcl-over-slf4j</artifactId>
        <version>${org.slf4j-version}</version>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
        <version>${org.slf4j-version}</version>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.16</version>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>javax.inject</groupId>
        <artifactId>javax.inject</artifactId>
        <version>1</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>servlet-api</artifactId>
        <version>2.5</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>javax.servlet.jsp</groupId>
        <artifactId>jsp-api</artifactId>
        <version>2.1</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>
    <!-- Communication to PowerTAC Server -->

      <dependency>
      <groupId>joda-time</groupId>
      <artifactId>joda-time</artifactId>
      <version>2.0</version>
    </dependency>
    <dependency>
      <groupId>com.thoughtworks.xstream</groupId>
      <artifactId>xstream</artifactId>
      <version>1.4.1</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
    <groupId>javax.jms</groupId>
    <artifactId>jms-api</artifactId>
    <version>1.1-rev-1</version>
</dependency>
<dependency>
    <groupId>org.apache.activemq</groupId>
    <artifactId>activemq-all</artifactId>
    <version>5.5.1</version>
</dependency>
<dependency>
    <groupId>activecluster</groupId>
    <artifactId>activecluster</artifactId>
    <version>20040423.075722</version>
</dependency>
<dependency>
    <groupId>xmlbeans</groupId>
    <artifactId>xbean</artifactId>
    <version>2.0.0</version>
</dependency>
<dependency>
    <groupId>javacc</groupId>
    <artifactId>javacc</artifactId>
    <version>4.0</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-jms</artifactId>
    <version>3.0.6.RELEASE</version>
</dependency>
<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>
<dependency>
    <groupId>org.jboss.spec.javax.ws.rs</groupId>
    <artifactId>jboss-jaxrs-api_1.1_spec</artifactId>
    <version>1.0.0.Final</version>
</dependency>
<dependency>
    <groupId>org.jdom</groupId>
    <artifactId>jdom</artifactId>
    <version>1.1.2</version>
</dependency>




    <!-- Sun Mojarra JSF 2 runtime -->
    <dependency>
        <groupId>com.sun.faces</groupId>
        <artifactId>jsf-api</artifactId>
        <version>2.0.3</version>
    </dependency>
    <dependency>
        <groupId>com.sun.faces</groupId>
        <artifactId>jsf-impl</artifactId>
        <version>2.0.3</version>
    </dependency>
    <dependency>
        <groupId>javax.validation</groupId>
        <artifactId>validation-api</artifactId>
        <version>1.0.0.GA</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-validator</artifactId>
        <version>4.0.2.GA</version>
    </dependency>
      <dependency>
       <groupId>org.hibernate</groupId>
       <artifactId>hibernate-core</artifactId>
       <version>3.3.2.GA</version>
    </dependency>
    <dependency>
       <groupId>org.hibernate</groupId>
       <artifactId>hibernate-annotations</artifactId>
       <version>3.4.0.GA</version>
    </dependency>
    <dependency>
       <groupId>org.hibernate</groupId>
       <artifactId>hibernate-commons-annotations</artifactId>
       <version>3.3.0.ga</version&g,t;
    </dependency>
    <dependency>
       <groupId>org.hibernate</groupId>
       <artifactId>hibernate-entitymanager</artifactId>
       <version>3.4.0.GA</version>
    </dependency> 
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.7</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>javax.ejb</groupId>
        <artifactId>ejb-api</artifactId>
        <version>3.0</version>
    </dependency>
        <!-- PrimeFaces component library -->
    <dependency>
        <groupId>org.primefaces</groupId>
        <artifactId>primefaces</artifactId>
        <version>2.2.1</version>
    </dependency>
    <dependency>
        <groupId>org.powertac</groupId>
        <artifactId>server-interface</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </dependency>
  </dependencies>
  <packaging>war</packaging>
  <properties>
    <java-version>1.5</java-version>
    <springframework-version>3.0.5.RELEASE</springframework-version>
    <springwebflow-version>2.3.0.RELEASE</springwebflow-version>
    <springsecurity-version>3.0.3.RELEASE</springsecurity-version>
    <org.slf4j-version>1.5.10</org.slf4j-version>
  </properties>
  <groupId>org.powertac</groupId>
  <version>0.0.1-SNAPSHOT</version>
</project>

No meu IDE (Springsource Tool Suite), recebo o seguinte aviso

Quando faço algo como "compilação mvn" no meu shell, ocorre o seguinte erro:

[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building xcz 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[WARNING] The artifact javacc:javacc:jar:4.0 has been relocated to net.java.dev.
javacc:javacc:jar:4.0
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.193s
[INFO] Finished at: Sun Dec 04 10:11:47 CET 2011
[INFO] Final Memory: 9M/160M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project xyz: Could not resolve depend
encies for project xyz:war:0.0.1-SNAPSHOT: The following a
rtifacts could not be resolved: maven-plugins:maven-cobertura-plugin:plugin:1.3,
 maven-plugins:maven-findbugs-plugin:plugin:1.3.1, Failure to find maven-plugins:maven-cobertura-plugin:plugin
:1.3 in http://repository.primefaces.org was cached in the local repository, res
olution will not be reattempted until the update interval of prime-repo has elap
sed or updates are forced -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e swit
ch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please rea
d the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/DependencyReso
lutionException

Quando insiro os plug-ins mencionados abaixo e façomvn site a seguinte mensagem de erro ocorre:

[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building xyz 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
Downloading: http://repo1.maven.org/maven2/org/primefaces/primefaces/2.2.1/prime
faces-2.2.1.pom
[WARNING] The POM for org.primefaces:primefaces:jar:2.2.1 is missing, no depende
ncy information available
[WARNING] The artifact javacc:javacc:jar:4.0 has been relocated to net.java.dev.
javacc:javacc:jar:4.0
Downloading: http://repo1.maven.org/maven2/org/primefaces/primefaces/2.2.1/prime
faces-2.2.1.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.609s
[INFO] Finished at: Sun Dec 04 10:35:51 CET 2011
[INFO] Final Memory: 9M/160M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project xyz: Could not resolve depend
encies for project xyz:war:0.0.1-SNAPSHOT: The following a
rtifacts could not be resolved: maven-plugins:maven-cobertura-plugin:plugin:1.3,
 maven-plugins:maven-findbugs-plugin:plugin:1.3.1, org.primefaces:primefaces:jar
:2.2.1: Failure to find maven-plugins:maven-cobertura-plugin:plugin:1.3 in http:
//repo1.maven.org/maven2 was cached in the local repository, resolution will not
 be reattempted until the update interval of central has elapsed or updates are
forced -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e swit
ch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please rea
d the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/DependencyReso

Qualquer ajuda é altamente apreciad

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