I can't find any mention of UPnP capability for 2Wire. So it looks like port forwarding may be necessary. That would mean setting up a static ip 1st, then forwarding a port for that particular computer. (Each comp on a network that also used LW would require a different port to be forwarded for it.)

1. Set up a static ip.
2. Forward port 6346: http://www.portforward.com/routers.htm

3. Within LW: Manual port forward instructions & sample image & 2 posts after that.

You can double-check to see if this port is open by using your browser go here: http://www3.limewire.com:6346/ The page should say 'Your test worked!'. What happens when you go there?