It it helps, I am willing to work on a test case written with Hibernate/Java only which demonstrates the issue.
I have not, because, this is is a design issue that can be explained without computer and it is probably best to think about it when comfortable on a couch.

http://jira.grails.org/browse/GRAILS-11645 - contains a unit test example which removes most of the Grails/GORM and uses Hibernate more directly.