We are seeing the following NPE (eventReceiver is null) as you read below.

Just before, we observe that the EventClient is calling removeNotificationListener and set the eventReceiver to null (I am looking where this call is made).
So it seems that there is a window for which the eventReceiver is null and the fetch result is processed.
Is it the case ?

Even if it's part of the normal closing sequence, I'd recomment to not print such a NullPointerException because it's fairly frightening; the user might think something that's not under control occurred.

Jan 25, 2008 5:22:17 PM EventClient removeNotificationListener
FINER: with all arguments.
Jan 25, 2008 5:22:17 PM FetchingEventRelay setEventReceiver
FINER: null
Jan 25, 2008 5:22:17 PM EventClient stopListening
FINER: non listening

FINEST: got exception to deliver notifs to the EventClient.
java.lang.NullPointerException
at com.sun.jmx.remote.ws.event.FetchingEventRelay$MyJob.task(FetchingEventRelay.java:298)
at com.sun.jmx.remote.ws.event.RepeatedSingletonJob.run(RepeatedSingletonJob.java:69)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:674)
Jan 25, 2008 5:22:17 PM FetchingEventRelay -MyJob-isSuspended