Try the following link, it's worked for many before apparently (I saw it in more than one thread):
http://www.gnutellaforums.com/showth...threadid=25673
As a last resort, you could perhaps try an uninstall app such as norton cleansweep.
Hope that sorts out your issue. (And I'm only a macman LOL.)
The answers were already in the forum, all anybody had to do was search for them.