Solution for me was, login modul is deployed as jboss modul. No packages from my login module are included in any deployments!.
my login modul is defined in standalone.xml as global, so any class loaders can find it.
I still had to add my login modul as dependency to some othe jboss provided modules... you see while testing which modul get problems, so you add your login modul to this modul as dependecy...