It was running fine on Cable TV, and suddenly when turned on, the channels are gone and we get a snowy screen.

You might have been disconnected....If you have tried a channel scan and nothing works call your cable company and have them come out and take a look.

Do you have a digital cable box? If that is the case you peobably have a bad splitter somewhere that is old. You might have aa bad end as well. I would call your cable company and tell them what is going on, tell them you are totally out of service and they will make it a priority.

Did you try a new channel scan? Perhaps there was a power failure and the TV lost all its channels from memory.

Go to the setup and initiate a new channel scan.