Have you tried it without jbpm? I am not sure that jBPM is the cause of this problem. I have seen this many times for regular web applications.
I'm inquiring on that subject...
I eliminate lot's of library including JBpm and now I'm suspecting CGLib to be the cause of that classloader leak...
But for the moment, I can't eliminate it completely, it is used to weave some aspects on concrete classes...
are you using Sun JVM? I suggest you to try to execute the same application with jrockit 1.6, if you continue to get the same error instal Jrockit mission control, is a powerful tool to analyze memory leak with Jrockit JVM.