i think your talking about a cable modem


do a few things..
unplug the usb cable..
1 unplug power of all devices modem, pc(turn off the pc first and copy the instructions), router. wait about 2 mins and plug it all back in.
2 reinstall nic drivers if it is on board then reinstall mobo drivers and chip set drivers.
3 if you can get one pick up a new straight through cable to see if it is the cable that is bad.
4 if all else fails call your isp and tell them.. it may be a faulty modem