[pgsql-admin] JCR (Apache Jackrabbit) locking when using Postgres, not with MySQL

Hello.
The subject says most of what I know at this point.

We are still not getting along with Apache Jackrabbit.
After a few hours of using Postgres as the Persistence Manager, the JCR gets stuck, apparently on a simple DB update statement.

This problem does not occur at all if we substitute MySQL!

This is Postgres v9.1.3 on RHEL5, 64-bit.

Thanks.