Junit blocked?

I am not sure if anybody else meet the problem.
When I run JUnit tests in 944, in most of the time the JUnit support is blocked(seems paused) showing "starting...", and it will never run the test
(i traced it and found even "setUp()" isnot invoked). I must force to stop it and re-run it, and re-run several times, and it would happen to run by chance one time.

I dont know whether it's a bug? It bothers me a lot.
Thanks.