The missing class can be found in the server/default/deployers/jboss-aop-jboss5.deployer/jboss-aop-jdk50.jar file, add that to your classpath. (I have found that the jars in 5.0 beta 1 are not packaged all that well, not everything is in jbossall-client.jar, like it should be. But then, it is a beta...)
thanks that helped. I also had to add trove.jar in the same directory.