I'm experiencing the same symptoms with my application that you describe. I'm using 3.0.7 though. It appears that the server simply stops sending messages. There are no exceptions displayed. In fact I found you message search for a solution to this problem. Well, maybe someone else will chime in with a solution.
Just a guess, but I suspect that 3.2 (CVS) version works better with respect to message expiration. I put a fix in that will expire (when reading) messages from the message queue, which will eliminate JBoss from having to load the whole body from disk. My changes also will expire messages in a background thread, so even if the messages aren't being actively processed (no clients), they get eliminated over time.
I don't know if you're working with lots of about-to-be (or already) expired messages, or if they just happen to be expiring next year, for example.
You should explain your situation better...
If you don't _mind_ upgrading, I suggest you go with 3.2.1, and go with the latest jbossmq.jar from the 3.2 branch.