Hi,
I see that you posted the question also here: https://community.jboss.org/message/531485
There are two things that come to my mind:
1) some wrong jboss client JAR, which is not matching the server version, is referenced
2) you wrote that you have two jar files, one with EJBs and the other with MDBs. Both are bundled in an EAR file, are they? Maybe this causes trouble. Could you try to combine those two files?
And maybe it is a strange configuration issue. So post as many details (code/config snippets) as possible.
I found another thread with the same error message. Maybe the logging hints in this thread help further: https://community.jboss.org/message/410897
Best regards
Wolfgang