Have you ever had LW on your computer previously?
If yes, delete the LW preferences folder; Point #2 & 3 in Fixes for Limewire (sample image included at bottom of page.)

or if Vista delete the whole LimeWire folder found in preferences folder http://www.gnutellaforums.com/genera...der-vista.html

I'd also recommend instead installing this Offline version of LW; http://www9.limewire.com/download/LimeWireWin-full.exe unless you need LW 4.18

If still problems see http://www.gnutellaforums.com/333278-post2.html