I have the tivo premiere using the comcast cablecard. The tivo is just a couple of months old. All channels work fine except HBO and Showtime and I get a "not authorized to receive this channel" on the screen. I have had comcast tech out and they have tried a few other cablecard they are telling me there is a problem with my tivo. Again all other channels work find except the two premium channels which I have confirmed with comcast I should be receiving. Suggestions?