Have you updated Java since you were using 4.12.15? Some people have had weird problems with the 2 latest Java updates 1.6.0_01 & _02. You could try this version instead. Use the JRE offline installer & remove your current Java version before you install this one.
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11

Also, delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used much 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.
http://www.gnutellaforums.com/genera...der-vista.html

Have you tried the latest LW (4.14.8)? See if that behaves any differently. Make sure that you download the offline installer. When you click to download & the download box pops up, cancel it. Now you'll see the option to download the offline installer
Lime Wire » Download LimeWire



If nothing works, send me a PM & I'll give you a link to download 4.12.15 basic again