When I came home this evening, my sone told me the TV upstairs had black all around the picture.
So I go upstairs and sure enough the picture is very small, about 25% of the screen. I tried a few menu items and noticed that when in the guide and the pciture moves to the upper right corner, exiting from the guide leave the picture in the upper right corner. Where ever the guide/menu placed and sized the screen, that's where it would remain when exiting back to live TV.
I tried several settings and nothing made the size of the picture correct itself.
So I used the In Home Agent, rebooted the box and it came back ok.
DVR's are basically just little computers. They have a hard drive, software and processor. And just like computers, they sometimes have little glitches that require a reboot. There are any number of things that can cause the problem but so long as it is not a frequent problem, I wouldnt be too concerned.