Have you gone through the fixes here (including rolling back Java, deleting preferences folder & replacing gnutella.net file)? There's a newer Java update 1.6.0_04 now, I'm using it & LW runs normally...you could try that one from the update Java link in the thread below. Remember to only have 1 Java version installed at a time.
If LW Will Not Connect

If you're sure that you've done all of those things correctly (with LW properly closed & restart afterwards), try the fixes below. The post's really old but a couple of people have recently found that it's fixed their problem.
http://www.gnutellaforums.com/78282-post22.html

What's the model number of your Belkin? When you set up port forwarding, did you use instructions from this site
PortForward.com - Free Help Setting up Your Router or Firewall
& did you make sure to set up a static IP address first? You also need to make sure that LW's listening port, port in the 'manual port forward' box & port forwarded within your router's config pages are the same number