Came across an interesting scenario.
Had a pre-running test case. And then removed the @Test annotation from it, and voila!

It seems JUnit developers really thought of this scenario where a developer un-annotates a test method and they gave an appropriate exception!

Well this seems to be an eclipse bug.It occured when I copied a window eclipse shared project and tried to run it.
I could not overcome this error till date, using following resolutions:

1/ Exclude junit3.3(NA)
2/Remove extension from TestCase.(NA)
3/Remove duplicate junit jar from the project.(NA)

~rohit.