Not positive, but looks like you must be adding yourself as a notification listener directly to the detector and handling the notification for a new detection? This was not the original intent of the notifications from the detector (really just added for the DetectorUtil class), but should work for what you are doing (most people use the MBeanTracker since makes the code a little easier).
So I wrote a simple test and found that there is a bug with this. I have fixed the bug and checked it in along with the simple test case. If you get the latest code at the 3.2 branch (the tag is Branch_3_2 on the jboss-3.2 module), will see there is a new directory under jmx-remoting/test/org/jboss/test/mx/remoting called simple. In this will be a readme.txt file with the sample code. Should have everything you need to get started.
I should also note that this current implementation is not from the JSR 160 JMX Remoting specification (something we are working on). However, all the code should work for any remote JMX calls you need to make.
Let me know if you have any other questions.
After your fix it is working now.