I have been having the EXACT problem you are experiencing for the past week and a half. I am in the SW area of St. Louis County in MO. Charter is finally sending me a tech for a service call this coming tuesday. I'll let you know of the results. From the sounds of it, it is either a problem with signal strength or a corruption of the processor that runs the picture to the TV. My experience is the following:
In St. Louis, MO:
Live TV works somewhat on some channels.
Movie tier channels work OK for the most part, with some pixellation.
Basic network channels (Fox, NBC, etc.) are extremely difficult to watch without getting frustrated, but the program can be understood as long as you don't need to hear all of the dialogue.
The higher cable-only channels like Spike TV and Discovery are not watchable, constantly scrambled.
Recordings of ANY channels are even worse than watching the same program live.
It should be known that my On Demand programming is working next to flawlessly, I watched an entire movie tonight with only 5 seconds of pixellation the whole time. Now the TV is again tuned to Fox, and it is not watchable.
Again, I'll post with the results of our service call on Tuesday.