Sorry it took a while to reply
I'm using version JBoss 2.4.3 and MQSeries 5.1.
Also, I disabled the JBossMQ mbean - it it possible that there is some interaction going on between JbossMQ and MQSeries as JMS Providers?
If jboss (in 2.4.3) does not find a queue it creates one in the JBossMQ implementation. Have a look at your server.log - Also having a look using the JNDIView of your server might reval something - you usually get at it on http://localhost:8082 and looking for the JNDIView mbean - and then select the list button on the page that is loaded.
Let me know how you get on.