Have you recently updated Java? Some people have had problems with LW when using the latest Java updates. Try this version instead. Download the JRE offline installer & remove any other Java versions before you install this one.
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11

If that doesn't help, delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used older versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire
This will kill all of your settings within options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.
LimeWire Pref Folder in Vista

You could also try installing the latest version of LW (4.14.8). When you download LW, use the offline installer (when you click to download & the box pops up, cancel it...now use the option of downloading the offline installer).