I have two PC's connected to the net using the BEFSR41 router which has been working fine now for 20 months. On NTL BB 750k. The router has the main PC (first connected to NTL cable modem) MAC address cloned in. Have you tried click on Control Panel then Network connections then click on LAN. Select
Support then try click on Repair. Also try shifting your ethernet connection cable into a different router port.