Hi David,
Note that the changes for JBREM-1292 "ServerInvoker should use a ConcurrentHashMap to store callback handlers" might help. Those changes are currently committed to the 2.2 branch.
As for the dump, it looks like you created it using the AS console, right? The reason I say that is that there doesn't seem to be an indication of which threads are holding the locks, and, if I recall correctly, that's a shortcoming of creating dumps from the AS console. If you could create a dump using kill -3, that would be a lot more useful.
Thanks,
Ron