This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
Please post the full stack trace for the error. Make sure you post only the first exception stack trace from the console log. Do not post the "Deployments in Error" report as that it usually useless in identifying the root cause of problems. Also post the version of JBoss AS, OS and JVM.
Alternately, you could attach the server.log and boot.log files.