First of all, delete LW's preferences folder. See the thread below (click on link) for instructions. If you've deleted the prefs folder properly, you'll go through LW's setup wizard again when you restart LW.
If that doesn't fix things, delete or replace the gnutella.net file (instructions for that in the thread below as well). Otherwise, try the other fixes there.
If LW Will Not Connect
If nothing there helps, please post back with your system details.