I've might found a bug: the Problem is, that none of the hibernate properties changes in the hibernate.cfg.xml file were considerated - only via .properties file.

when you look at org.jbpm.db.Configuration#createConfiguration(String configResource):

the properties gets overridden:
configuration.setProperties(hibernateProperties);
better append the changes from the properties file:
configuration.addProperties(hibernateProperties);

The second thing is, that the configure() call is executed before the properties file gets considerated. So it might be better starting the configurate() at the end of this passage.

I dont know how this is managed in 3.1 because I am still working with 3.0 - throwing a first glance at the code caused only heavy confusion ;)