The jBPM 'websale' sample application fails - when an order is approved (OK is selected). This exception is displayed back to the user:

Error completing task: An exception of type "org.jbpm.graph.def.DelegationException" was thrown.
Closing the database context failed: An exception of type org.jbpm.JbpmException was thrown, with the message: problem closing services

{persistence=org.jbpm.JbpmException: setRollbackOnly was invoked while configuration specifies user managed transactions}

The server.log is attached.