Okay this is very easy to fix,

STEP 1. shut down limewire

STEP 2. DO NOT delete with your preferences folder, instead only delete gnutella.net file from that folder if your having this problem it should only be 1kb in size.

STEP 3. download zSHARE - gnutella.net (this is your new gnutella.net file)

STEP 4. put the new gnutella.net file in your preferences folder (notice it is around 20kb in size)

STEP 5. restart computer, start limewire (if it doesn't connect right away, wait a couple of minutes)

let me know if this fixes the problem.