It's only proven to be a temporary fix for me. I don't know how it's done in other operating systems, but in Win XP open Windows Explorer and find the default copy of the gnutella.net file from your installation of LimeWire. Mine was in the C:\Documents and Settings\username\.limewire directory. Copy the gnutella.net file from this directory, then navigate to C:\Documents and Settings\username\Application Data\Limewire and paste it over the one already in that directory.

I found out how to do this from the faq's and stickies in this forum.

Hope this helps.