Try updating your Java: Java SE Downloads
Download the JRE offline installer & remove any other Java versions via Add/Remove Programs (in Vista I think it's Start > Control Panel > Programs > Programs & Features) before installing this one.

Next, 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 change 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.
Vista users: LimeWire Pref Folder in Vista

If that doesn't help, right click on the LW icon > properties > compatibility. Try running in compatibility mode for XP.

If nothing there helps, try reinstalling LW. See LOTR's tips here: http://www.gnutellaforums.com/320995-post377.html