Sounds like either the STB hasn't been added to the account, or the hit (provisioning message to the smart card) didn't get through. If you'd like to PM me your account number, smart card number, and STB number I'll have a look for you. The STB number should be on the box the STB came in, or on the bottom of the STB itself and will start either 03xxxxxxxx or 10xxxxxxxx.
One of the team can confirm I'm an ntl associate.
EDIT: Oooh, 1000 posts!