1. It sounds like a java problem. Might I suggest you backup your Java installer. Then go to the Add/Remove Control panel, remove all Java versions listed be they called java or jre, etc. Then install the Java 1.6 Beta
http://java.sun.com/javase/6/download.jsp JRE "Offline" version which is a 15.72 MB download. It's had very good reports.
2. Also, download the "Offline" version of LimeWire from here (or your pro page):
http://www.limewire.com/english/content/download.shtml
3. Again, delete any LW prefs folder that might have been created. Make sure you do step 3 in deleting your LW prefs folder behind the "Hidden" Apps & Data folder.
4. Make sure all your screensavers are turned off. Then start LW up.