Lately I installed GWT Designer for Eclipse Helios (3.6). I wanted to check it's features. They aren't so cool I've expected but that's other story. The problem was that suddenly my main GWT enabled project began to freeze during compilation. The project is maven enabled also.
So it freezed in about half of compilation. All other features of Eclipse worked well. Restarting Eclipse and Windows didn't help anyway.
After about an hour of investigating I've found that GWT Designer caused this. After removing it all came back to order.
Ofcourse I suspect that something is wrong with my Eclipse for example I have too many bizzarre plugins installed but if I could have such problems you could have them too. So be warned :-)