Are you using Java 1.6? You'll need to.
Use the JRE offline installer & remove your current Java version before you install the new one.
http://java.sun.com/javase/downloads/index.jsp

Lots of people have had trouble with McAfee.
A lot of people have uninstalled McAfee (or parts of).
http://www.gnutellaforums.com/showthread.php?t=66843

But this poster found a solution & is now able to run LW with McAfee
A fix for Visat/Limewire