If you're using NIS then it's best to disable XP's firewall since they're known to interfere with each other. To configure NIS to allow LW full access, see: Configuring Norton Internet Security

Do this simple test for us. Using your browser go here: http://www3.limewire.com:6346/ The page should say 'Your test worked!'. What happens when you go there?

Hopefully your Belkin router utilises UPnP technology. Wireless routers often don't. If not you may be best to forward a port for LW. If you do need to do this then you can find instructions here: http://www.portforward.com/routers.htm
The process involves 1. Setting up a Static ip (most important for this to work.) 2. Forward port 6346. 3. Within LW: Manual port forward instructions & sample image & 2 posts after that.

Tell us how you go.