Postgres and Jboss using two postgresql databases

Hi,

I'm using two postgresql databases (one version 8.0, one
version 8.2) with JBoss AS (version 4.2.2.GA).
We have just migrated to JBoss 4.2.2.GA.
We get lots of exceptions in the JBoss logfile after
migration. Seems there is a problem getting data
from both databases in the same method (using an EJB3
Stateless Session Bean).
One database call is made via JDBC (through a DataSource
object), the next call (to the other database) is done
via another Stateless Session Bean (throguh the Entity Manager
object).
Earlier (with the older version of JBoss) - this has not been
a problem. Searching for an answer I've seen suggestions that
the errors might come from the fact that postgresql does not
support 'two-phase commit'.

Any idea what I could do? 8.1 is said to support 'two-phase
commit' - I'm not sure how to configure it. Not even sure if
this is the source of the problem.

/Best regards, Håkan Jacobsson