Did you resolve your problem?
I have the same problem.
I have an application running in jboss 4.0.4GA using EJB 3 and other application running in jboss 4.2.1GA using EJB3 too.
IÂ´d like to know when the 4.2.3 version will be available?
I can confirm this solution. In my JBoss IDE, I had a 4.2.2 server installed. When I ran a JUnit test case to look up an EJB running inside the server, I received the same exception mentioned above. I then installed a version of the 4.2.3 server onto my local file system in a different directory. After this, I went into my IDE settings: Window -> Preferences -> Server -> Installed runtimes -> Edit -> and pointed the home directory to the 4.2.3 server. After the IDE resolved it's references to the new server path, I was able to run my JUnit test case successfully. (It goes without saying that I had to deploy my project as an ejb jar to the 4.2.3 server, and then start the 4.2.3 server before running the test case)