This has been ongoing for so long, I've lost track of time. When I watch some DVRd shows, they playback with sporatic pixelation. When the option is available, I switch to on Demand, and there are no pixels; this leads me to believe that it is just my DVR.
Before you say it is the channel, I can say that it is not, as it is not always the same channel.
Also, live TV does have this issue, but not quite as often, and not the same channels as the DVR playback.
My DVR is full of things I haven't watched yet, so I'm not looking to trade it in and lose it all just yet.