FailedConsole Output

maven31-agent.jar already up to date
maven31-interceptor.jar already up to date
maven3-interceptor-commons.jar already up to date
<===[JENKINS REMOTING CAPACITY]===>channel started
Executing Maven:  -B -f /var/lib/jenkins/workspace/taverna-maven-parent-maintenance/pom.xml -Dmaven.repo.local=/var/lib/jenkins/workspace/taverna-maven-parent-maintenance/.repository clean install
[INFO] Scanning for projects...
[INFO] Initializing Artifactory Build-Info Recording
[HUDSON] Collecting dependencies info
[INFO] 
[INFO] Using the builder org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder with a thread count of 1
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building Taverna Maven parent 2.6-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] Downloading: http://repository.mygrid.org.uk/artifactory/repo/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.pom
[INFO] Downloading: http://repository.mygrid.org.uk/artifactory/repo/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.881 s
[INFO] Finished at: 2014-05-14T16:33:57+00:00
[INFO] Final Memory: 10M/69M
[INFO] ------------------------------------------------------------------------
[ERROR] Plugin org.apache.maven.plugins:maven-clean-plugin:2.5 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-clean-plugin:jar:2.5: Could not transfer artifact org.apache.maven.plugins:maven-clean-plugin:pom:2.5 from/to mygrid-repository (http://repository.mygrid.org.uk/artifactory/repo): Failed to transfer file: http://repository.mygrid.org.uk/artifactory/repo/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.pom. Return code is: 503 , ReasonPhrase:Service Unavailable. -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[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 read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginResolutionException