Looks like a bug because this only happens after a restart of JBoss, or a jar deploy. After that, the collection in the relationship is not usable.
To get back, I drop all 3 tables in the db, 2 ejb tables and the relationships table.
Everything then starts working fine again.
I have the same problem, but I not know what's wrong!
Are you using the alpha release or tip? There were a couple of days when this was broken in tip, and then I disabled the code (haven't gotten to fixing it yet). I think it is still disabled.
What is tip?
I have download jboss-all from sourceforge with cvs.