Error when running scheduler: org.jpox.exceptions.TransactionNotActiveException: Transaction is not active

The attached exception occurs when trying to run a schedule. The error prevents the schedule from running and as a result all
builds associated with that schedule do not run! Builds need to run manually which defeats one of the main reasons of having a CI server.

This problem existed in version 1.2.3 and I was hoping that a fresh install (new database) of 1.3.3 would eliminate the problem.
However, week after the upgraded it started happening again.