You'll need to be using Java 1.6. Reinstall Java & use the JRE offline installer & remove your current Java version before installing the new one.
http://java.sun.com/javase/downloads/index.jsp

If you're using McAfee, there have been some issues with that
http://www.gnutellaforums.com/showthread.php?t=66843
A fix for Visat/Limewire

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