Delete your LW preferences folder. Instructions here
http://www.gnutellaforums.com/showth...threadid=36420
(this will delete all your settings within tools > options, so if you're not sure of what they are, make a note of them all so that you can reset them later)

Uninstall your Java & reinstall as per the instructions in the above thread. Or you can try the Java 1.6 (JRE) beta here
http://java.sun.com/javase/6/download.jsp