I'm going through this right now too. I had my Motorola modem for 5 years or so and it worked fine. When I moved into my new apartment at the beginning of the year, Comcast insisted on giving me a new modem. I've had nothing but problems ever since. It's a Cisco modem. It stopped recognizing my cable input and they weren't able to reset it over the phone. They couldn't connect to it at all. So I went in to comcast and got a replacement. Another Cisco unfortunately. Less than a month later, this one started doing the same thing. I have to unplug the electrical outlet and twist the cable outlet a few times an hour. Sometimes it takes me several attempts.

A couple of months ago I went online to see if people had problems with Cisco modems in general but didn't see anything. I also went to Best Buy to look at their modems but they only have 2 or 3 cable modems. Yesterday I decided to switch to DSL and went to AT&T's website to check it out. But their price is comparable to Comcast and the speed is a lot slower so I'm back to the drawing board.

If you're having problems with your tv though, that's not due to your modem.