I have seen people complaining about this exception and it turning out to be a issue with how the application was packaged. So far i haven't seen a post where this turned out to be an issue with the way JBoss deploys the application.
If you think, it might be related to JBoss than the packaging, please post more details including the exception stacktrace, the output of:
jar -tf yourapp.ear
and the version of Java you are using and also the tool or script which you use for creating the ear.
And does this happen when you are redeploying (hot-deploying) the application?