laptop not connecting to router-using cable others fine. . .

I have a laptap that I connect to a D-link router and it suddenly stopped working. I have another laptop that when I plug in to the same cable works fine. Yet when I plug the first laptop into the modem directly it gets connection and works fine. I brought the laptop to a firiends and tried setting it up through his router but again it would not work. Plugging it in to his dsl modem again it works fine directly. I have run network setup multiple times to no avail. When I run it and it is plugged into the modem it goes through without a hitch but when I have it plugged into a router I have to select the network card as "ignore disconnected hardware". Again all other computers connect fine but not the laptop. Does anyone know a reason that a computer would not be able to connect to routers alone?