It possibly means your entitlement to use the TVDrive service has been removed (e.g., if you're not being billed for it). Check the front panel - does it say Live TV? If not, give Customer Services a ring on 150 from an ntl phone line - a signal can be sent to re-enable it remotely.
Alternatively, the hard disk drive inside the box might have failed. This will require a box swap to fix, and you will lose all your recordings.
