I noticed something tonight. So, I have a show recording from 7:30-10:00. And I wanted to record a 2nd show at 8:00 but not watch anything till later. I waited till 8:00 to see what happened. At 8:00 the PVR box displayed the second channel number, meaning it tuned to that channel, but it didn't record. I went to that 2nd channel and pressed the "record" button, and both shows are recording now. So it tuned to the 2nd channel but didn't automatically record it. And, yes, sadly it's out of warranty. I had 3 years and the PVR is more than 4 years old.
This sounds like it could be hard drive issue... I would suggest watching all your programs you have on your hard drive, and do a full format. If you want the instructions to fully format the pvr back to factory, just let me know and I'll post the instructions (can be done via remote!). Please keep in mind that this COMPLETELY erases ALL recordings on your hard drive.