Some times when I redeploy a SAR after I've made some changes to the code inside the SAR JBoss does not run the newly deployed code but the old code. The only way I have found to get JBoss out of this state is to deploy an EAR file (the code in the EAR has no dependency on the code in the SAR or vica verca).
I have not managed to spot a pattern to reproduce the problem. I don't see any exceptions or errors either.
I also looked inside inside a class file in the SAR to make sure that the new code is in the SAR (I searched for a known string in a class file).