Try deleting LW's preferences folder when LW's properly closed. Points 2 & 3 in the thread below have instructions.
Fixes for LimeWire

I'm not really sure whether changing compatibility will help but you could try it if you like (point 5).

If nothing works, try reinstalling LW but make sure to use the offline installer, not the recommended one.
http://www.limewire.com/english/content/download.shtml