Mediacom might be your problem
[RANT] Mediacom blocking P2P traffic - Dont waste your money - dslreports.com

Just double check that your XP firewall is off & you could try reconfiguring the Norton firewall.
http://www.gnutellaforums.com/226610-post6.html
PortForward.com - Free Help Setting up Your Router or Firewall

Try changing ports. In LW tools > options > advanced > firewall config. Change LW's listening port to 64049 (or something in the range of 49152 - 65535) > Apply > ok.

Also delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used older versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire
This will kill all of your settings within options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.

What's the model of the D-Link router? It might have an internal firewall, so you could try port forwarding. Click on the link below, find the model in the router index, then choose LW from the list of programs. You'll get detailed instructions for port forwarding!
PortForward.com - Free Help Setting up Your Router or Firewall
Don't forget the step of setting up a static IP address, if that's part of the instructions. LW's listening port, port in the 'manual port forward' box & port forwarded within the router all have to be the same number