What model DVR?
This is often a symptom of a dying hard drive. What happens if you swap this "bad" DVR with one of your good DVRs? Does the problem follow the "bad" DVR, or stay in that room? This will help you isolate the problem to the DVR itself. If you verify that it's that DVR, then call DirecTV and request a replacement. It's free if you have their Equipment Protection Plan. Otherwise ~$20 for shipping.