No sure if this helps, but I found the csv sourceforge project jbpm.db to be of help. Basically it describes the recommended hibernate properties and the jdbc driver recommened.

i.e.

hibernate.dialect=org.hibernate.dialect.SQLServerDialect
hibernate.connection.driver_class=net.sourceforge.jtds.jdbc.Driver
hibernate.connection.url=jdbc:jtds:sqlserver://localhost:1433/jbpmtest
hibernate.connection.username=sa
hibernate.connection.password=test

hibernate.show_sql=true
hibernate.c3p0.min_size=1
hibernate.c3p0.max_size=3
hibernate.query.substitutions=true 1, false 0

and

jdbc driver=jtds-1.1.jar

jTDS claims that it works without a problem on MS SQL2005 hence I would assume its OK.

BUT, you might like to be aware of

http://jira.jboss.com/jira/browse/JBPM-326?page=all

Cheers, Andrew