Hard to say but possible cause would be:
your ejbCreate method encounters an uncatched exception, hence the creation fails and the container tries to roll back transactions.
If you're manipulating relations, there may be some exceptions too that cause this error.
I am getting the same exact error and for the life of me I can not figure it out. Only happens on Entity beans though.
If anyone has come across this one and have found the fix, please pass it on.