D-link you have the option of UPnP or port forward. I don't know that model, but most d-links do better port forwarded. See the UPnP section & look for Di-Link to find out how to enable UPnP: Connection problems? Check here first! (click on link) I presume you're using windows XP. If yes, make sure your XP firewall is configured to allow LW full access: Firewall configuration instructions (click on link). Your model should support UPnP. Let's hope it's a reliable implementation of UPnP. If you go here http://www.portforward.com/english/r...6/Limewire.htm you will see UPnP option under games & sharing. If this is not the same as your model, then you may have V.5, in which case look under Thompson here for your model http://www.portforward.com/routers.htm
Keep in mind those are port forward instructions which is the alternative to UPnP. But it does at least show you how to telnet into your device & where to find some of the options.

Modems/routers such as yours have internal NAT firewalls. UPnP will allow LW to request the modem to open a port when needed. Port forwarding is manually opening a port so it's always open when LW is open. (UPnP isn't always reliable depending on brand, etc.)