Strange dvr issue

My Dtv DVR has been pixelating at random times.

The strange part is that by pressing the 30 sec rewind, the pixelation goes away.

I've even had dvd players do this. When they used a processor that's almost, but not quite, speedy enough...

Or when there are a few bit errors in the stream.. some software/firmware can get horribly confused, yet hitting the skip-back button to a non-corrupted segment seems to sort things out.

I've noticed that here with various players.