Get rid of one of the Java versions that you have installed. Remove the older 1.5.0.6.

Make sure that you're not running 2 software firewalls...turn Vista's firewall off & just use the Norton.
You don't need to shut off the Norton firewall - just configure it so that it's allowing LW. If you've already added rules for LW, remove those & start from scratch - add LW rules all over again. See the links below for more info.
http://www.gnutellaforums.com/226610-post6.html
PortForward.com - Free Help Setting up Your Router or Firewall

Try changing ports. In LW go tools > options > advanced > firewall config. Change LW's listening port to 65000 (or you can try any ports in the range of 49152 - 65535) > apply > ok. If you've allowed a specific port thru your firewall, make sure that you allow the new port number.

The gnutella.net file's in the preferences folder, which is hidden by default. So you'll need to show hidden files & folders before you can see it. Check out this thread for how to do that: LimeWire Pref Folder in Vista

Otherwise, try the rest of the fixes here: If LW Will Not Connect