Does it work with default configuration?
Perhaps you could enable debug logging for both jBPM and hibernate, that can put some light on the issue. Your configuration file would be useful as well.
How does your hibernate configuration look like? Maybe it is set to create-drop?
I had the same problem and fix commenting this line in file jbpm.hibernate.cfg.xml
<!-- <property name="hibernate.hbm2ddl.auto">create-drop</property>-->