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

This person found a solution to their McAfee problem
http://www.gnutellaforums.com/general-vista-windows-7-later-support/68010-fix-visat-limewire.html