Have you removed any old versions of Java that were already on the computer? Have a look through this thread, as Grandpa says maybe another program is causing a conflict with Java?
http://www.gnutellaforums.com/showth...ighlight=mouse

Also have a look through this one, I know it's not exactly the same as your problem but you might find something helpful anyway. If not, post back with your details (see the questions LOTR asks) & any fixes you've tried that didn't work.
http://www.gnutellaforums.com/showth...ighlight=mouse

Somebody else will probably have more ideas about this!