I have a Proscan, PS32108, that does not display an image?

When I turn on the TV all I get is snow. I have a good cable source attached and the menu has been set for cable, but all I get is snow. I have even tried switching it to anntena but I do not receive any of the local stations either. The other problem that I had when there was a picture, was these diagonal white lines that appeared through out the screen. I'm not sure if that is related to my not having a picture now or not.