Some of my recordings of Olympics broadcasts won't play. I watch several minutes, then the playback stops and I'm back at the menu with the list of recordings. It kicks out at the same place whether I am watching, skipping, or fast-forwarding. It will not resume, either. I always have to start watching at the beginning. Out of dozens of recorded episodes, this has happened on four of them.
Do you have an x1 DVR? If you do, hold down the power button for 15 seconds and then let it power back up.
If you have the newer x1 DVR without the power button, unplug it for 10 seconds. Let me know if you can experience the full recording.