Try steps 1, 3 & 5 in the thread below
Fixes for LimeWire
(if you've used an old version of LW before, you might also have a preferences folder in the old location...see point 2)
If you need to reinstall LW, make sure to use the offline installer (not the reccommended one)
http://www.limewire.com/english/content/download.shtml