Is it a bug in the injection mechanism?
I have the same problem... This has worked in all earlier versions of EJB3 at least since summer 2005...
Is it wrong to use mutual dependencies?
it's seem like a new bug in the injection code which inserted during the the new release of JBOSS (jboss 4.0.4 GA version).
however you can use look up directly instead of injection in the places you have the problem with mutual dependecy.