Try a different port. Go to LW's menu bar, Tools>Options>Advanced>Firewalls & change the listening port to one between 49152 - 65535. A good one to try is 64049. Change it for the connection port also.
BTW your model router has major firmware problems. Which means it's unreliable to use in UPnP mode, & can still be unreliable anyway. See
http://www.gnutellaforums.com/showth...843#post196843