Grails, Hibernate and JPA: hanging application

When developing an application in Grails I’ve been adding a backend written for JPA. This should be no problem – you think. But while the unit test for the JPA backend work fine for themselves, when adding the backend to the Grails application, Grails hangs when accessing the EntityManager. It does not help that all my efforts to join the Grails mailing list with my gmail address have failed so far. I have no clue how to fix this problem which took most time out of my last weekend :-) Perhaps Hibernate does not like to act as a Grails ORM and at the same time as a JPA provider. Or I have JAR conflicts. Any ideas?

Update: It has been suggested that the problem might be that there are several incompatible ASM jars in the classpath.