RHQ management -- server plugin -- two X-Site related operations are failing.

The only information I was able to gather until now:

java.lang.Exception: JBAS011002: Failed to invoke operation: null, rolled-back=true
at org.rhq.core.pc.operation.OperationInvocation.run(OperationInvocation.java:278)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:679)