ok your modem has a USB connection and a cat 5 or ethernet or network cable connection ...or whatever you want to call it. You can not use both AND you can not use the USB since you are using the router because the USB ( if you have it connected ) goes from the modem to the pc. Since you have the router you need to disconnect the usb cable.
then turn all off, turn on the cable modem, wait 30 seconds or so , turn on the router, turn on your pc's
so this should be your set up ...coax cable from the wall to the modem, cat5 cable from the modem to the WAN port on the router. then either cat5 cable from the lan ports on the router to pc's / notebook...or wireless connections.
I left out power connections to devices, because that is assumed.