Apparently we now are expected to stay up 24 hours to watch programming on Comcast, since the signal is scrambled in the middle of the night, which is of course when people tape things so that they can watch them in the morning. My guess is that Comcast, in its never-ending quest to squeeze every last penny out of those of us unfortunate enough to not have other options like DirectTV, has hit upon this as a way to force people to rent even more of its over-priced equipment, i.e. a DVR. I expect predatory, anti-consumer behavior from Comcast, one of the world's most hated monompolies, but this is low even for Comcast.
Can you give a better explanation of what you mean by a scrambled signal? Maybe some local channel is broadcasting something special? Or maybe you have signal issues causing the picture to pixelate overnight?