Hot deploy not longer working on JBoss ("Scheme change not implemented")

I've got a pretty annoying problem with my JBoss AS 4.2.3 GA.

Until recently everything was running fine, but now the hot deploy feature is now longer working. And -- as always -- I don't know what I did to cause this behaviour.

My projects are built with Maven. I've cleaned every target directory, installed the projects and then deployed them to the server. So the sources in Eclipse and the deployed projects on the server should be identical. Inside a method I've added a simple System.out.println("test"); statement and -- BANG! -- I get the following error:

_{(source: imagefruity.com)}

Do you know a way out of my trouble?

Ok, I did the following things now:

1. Uninstall all JDKs
2. Install only one JDK, namely JDK5 (cause that's the one we use in production)
3. Clean, install and deploy every project anew

And now it seems to work (I'm keeping my fingers crossed).

I've used JDK 6 Update 20 for building in Eclipse and JDK 6 Update 7 in Maven. Maybe that has caused the problem.