Hi,
I faced the similar problem during jBPM 4.3 Spring 3.0 prototyping.
It is caused by missing <object class="org.jbpm.pvm.internal.id.DatabaseIdComposer" init="eager"/> statement in process engine descriptor.
The problem in jBPM is that it silently skips situations when core services are not configured and missing. I suppose that it is not possible to create a proper Execution without IdComposer, but still this situation is silently ignored.
Dmitry