You're on a cable service, and yet you have bought an ADSL modem/router???
You cannot use an ADSL modem/router with a cable service. The clue is in the name, really.
You need a router. Plug your modem into it. Remove all trace of your modem from your PC. Configure the router with your NTL connection settings.
At least you chose a very good modem/router, I'll give you that!