Have a look at this thread below. There are some instructions for finding the prefs folder, plus a few other fixes to try.
http://www.gnutellaforums.com/connec...t-fix-try.html

If nothing there helps, can you let us know the brand & model of your modem/router? You might need to look underneath, if nothing's showing on top. If you're using a wireless connection, the modem/router might be in another room