Try these fixes. Remember to make notes of your settings if you delete the preference folder. Everything will go back to default.

http://www.gnutellaforums.com/showthread.php?t=36420

If that doesn't work then try this Java Beta:

http://java.sun.com/javase/downloads/ea.jsp

If still stuck then post all details/info that you think might be relevant

It just leaves everyone guessing if you don't give more info

(The ones above are guesses as well)