We don't fully support AS 4.2 at present. We're working on that, but you should use 4.0.5 for now.
In the meantime, if you wish to try AS 4.2.0GA then you can look at the current code in subversion.
Kurt updated the jbossesb-server yesterday so that it is compatible with AS 4.2. Also, the quickstarts have been tested on AS 4.2.0 GA.
More information about what has been tested can be found in the following posting http://www.jboss.com/index.html?module=bb&op=viewtopic&t=110237