If you are using a ConnectionFactoryLoader (looks to me as if you are) there was a race condition that might have produced this problem. Fix is in 2.4.4 and 3.0. If this doesn't help show lots more config info and what happened before the error.
I was just looking through the JBoss Dev archive (not linked to from the JBoss site anymore, but I found the URL from Google's cache ;-)) before you wrote, and I saw the posts where you mention the race condition. I'm going to assume that this is the problem and hope that it doesn't reappear at some critical moment. Thank you for letting me know which JBoss versions have the fix!