I have been running into the same problem, the only solution I have found is to turn on the JBoss unified(flat) classloader.
Go to server/default/deploy/jbossweb-tomcatXX.sar/META-INF/jboss-service.xml
and change the UseJBossWebLoader value to true.
The side effect of this is that the first instance of a class that is loaded will be used by all applications in JBoss, so if you are using a different version of a jar in one app than a different one you may/will get unexpected results.
BTW someone else has the same problems we are