At a first glance, two things come to my mind.....
First, did you also upgrade your Java installation?? If not, uninstall LW and all Java versions on your system. Reboot and then download the JRE offline installer of the newest Java version from here:
http://java.sun.com/j2se/1.5.0/download.jsp
Install it and reboot again, then reinstall LW.
Second, you might have a corrputed LW preference folder.
Read here on how to delete this folder (Point #2 & 3 in Fixes for Limewire)
http://www.gnutellaforums.com/showth...threadid=36420
Afterwards reboot your computer.
Also, be aware that there are a lot of faked files flooding the network.
Read here about how to recognize them:
http://www.gnutellaforums.com/showpo...98&postcount=4 