Try steps 1 & 2 here: Try deleting your LW Preferences folder whilst LW is closed; instructions here: Point #2 in Fixes for Limewire (sample at bottom of page.)

Failing that, if you have LW 4.10 then follow these directions but exchange the name of FrostWire for Limewire: How to delete your FrostWire Preferences folder
ie: LW 4.10 changes the name & location of the preferences folder. You must view hidden folders in order to find it. It's found at C:\Documents and Settings\*yourusername*\Application Data\limewire