I use a D-Link 504G. When you forward a port in the device, be sure to save settings & reboot the router. Otherwise settings won't have been saved properly. Also, it's best to do a separate port forward for each of UDP & TCP.
Also did you set up a static ip. That's most important.
If you're using LW on 2 different computers on the same router, you'd need to do a separate port forward for each computer & 'must' use a different port number.
AFAIK Your model does support UPnP however I've had report from another or 2 that it doesn't work well. It may require firmware update to get this option anyway.
FYI here was my original instructions for port forwarding the D-Link 504G but these instructions were for Mac;
http://www.gnutellaforums.com/showth...highlight=504g