We need to clarify which Tivo you have because there are 3 models labeled Series 3, Tivo HD. Look on the back of the Tivo label, it should say what model number follows "TCD".
TCD648 = Series 3, 2 cable slots are in the rear
TCD652 = Tivo HD, 2 card slots are in the front
TCD658 = Tivo HD XL, "
The cards may be the problem, as well as the card slot. It may or may not get fixed. I suggest you not use the Tivo to watch netflix if that is what's causing the problem, if you have another device hooked to your TV. PS3, Wii, Internet enabled Blu-ray player, are some of other devices with Netflix.
Series 2 (PLS, sold)
TiVo HD 1TB (157 HD Hrs, PLS, "652")
Roamio! Oh, wait, Its Juliet!
OTA! OTA! OTA!
The TiVo Apocalypse begins on Sat 2013 Feb 16 00:00 GMT!