Bitter bites with Java

Hi,
Some of you might have come across the following strange exception when moving to Jboss5 from Jboss4.x.
Adding multiple last resources is disallowed. Current resource is [EMAIL
PROTECTED]
| 16:17:18,000 WARN  [JDBCExceptionReporter] SQL Error: 0, SQLState: null
| 16:17:18,000 ERROR [JDBCExceptionReporter] Could not enlist in transaction
on entering meta-aware object!; – nested throwable:
(javax.transaction.SystemException: java.lang.Throwable: Unabled to enlist
resource, see the previous [...]