Cannot connect to the internet.?

My friends computer has DSL, i just recently reformatted it and installed a new NIC and it has worked fine for weeks. Now he cannot get online, his modem is a Motorola 2210-02-1006 and the lights are solid except for activity and its blinking. He can do a ipconfig and receive his IP and he can ping his IP. The computer is connected directly to the modem, no router. He has checked the device manager and the computer sees the NIC but will not connect. Hes getting the inactivity yellow light on the Ethernet cable. What could be the problem? He has tried resetting the modem but is still having problem.