Which version of LW are you running?
I'd suggest you do these things:
http://www.gnutellaforums.com/333278-post2.html. (For you, get your installer from your Pro page, however you probably already have a copy on your desktop right?).
Also delete your LW preferences folder:
http://www.gnutellaforums.com/window...tml#post183932
'Generally' the answer to such fatal errors is running LW in a particular mode. See points 5 & 6 here:
Fixes for Limewire (click on blue link). If running Vista then choose XP compatibility. Also, whether using Vista or not, set it to run as Admin.