You are most likely having an issue with that box's Hard Drive.  If you have Power Cycled it by holding the button in for 6 seconds and it still does this on your recordings, try recording a show of about the same lenght and watch it while its recordings.  If there are no errors during the recording but when playing back, then the Hard Drive in the unit is fail.  Please call tech support at 800-288-2020.  We will have to do a little bit of trouble shooting and may even try a Diaster Recovery at which point you will loose all your current recordings.  If we have to dispatch out to you, the tech will end of probally replaceing the box anyway and you will loose them still.  There is an off chance that the issue is the line to the box, but you will need to call in to have us run some tests. 8 )