What versions of AS and JBoss Cache are you using?
Also, you should have access to the Customer Support Portal; it's may be better if you open a case there and communicate that way as you get a 2 hour SLA and can easily do things like attach logs. You got lucky here that I happened to check my e-mail folder with forum posts.
This is actually for Intuit, whom I believe you're familiar with. I am only here for another couple of hours. I've used the support portal quite a few times before, and have unfortunately concluded that it will not help me when time is limited... so the forum post was a shot in the dar. I will ask Bill DeCoste to follow up if the client is interested in further pursuing this.
I tested this with JBoss 4.2.0, with JBoss Cache 1.4.1 SP3 and hiibernate 3.2.3GA. I even tried dropping in the latest SP for JBC, but nothing changed.