When the testsuite is run, it always fails with:

BUILD FAILED
/qa/hudson_ws/workspace/eap5-as-rhel5-x86_64-sun6/src/jboss-eap-5.0-src/jboss-as/testsuite/build.xml:1403: The following error occurred while executing this line:
/qa/hudson_ws/workspace/eap5-as-rhel5-x86_64-sun6/src/jboss-eap-5.0-src/jboss-as/testsuite/build.xml:1497: Error starting server "profileservice": Server failed to start in time; see logs.

This is due to the previous running instance of AS wasn't shut down properly:

[server:stop] Shutting down server: all
[server:stop] Writing server thread dump to /qa/hudson_ws/workspace/eap5-as-rhel5-x86_64-sun6/jboss-eap-5.0/jboss-as/server/all/log/threadDump.log
[server:stop] Failed to shutdown server "all". Destroying the process.
[server:stop] Unable to shutdown server properly: org.jboss.jbossas.servermanager.ServerShutdownException: Failed to shutdown server.Process was destroyed.

Obviously the process destroying mechanism doesn't work that well.
It must be some deployed service that's stopping it from shutting down.

Note that this only happens on 64bit RHEL systems.