The last error looks like another Classpath problem.
You need to stick with one JBoss distribution. All three that you mentioned should work the same, but the jars and the contents of the endorsed directory may be different. If you have something that works with 5.1.GA, stick with that.
Whenever you start a client without using wsrunclient from the command line, you introduce the risk of getting the Classpath wrong. Unfortunately, in many cases, the problem turns out to be us or our code. :(