Could be, although it'd probably be a disk problem and then he'd have other symptoms too.
Whats happening is that the file system is becoming corrupt for that show entry, making it not play. When he reboots it, it does a file system check and tosses out the corrupt portions, which makes the show disappear.
Used to be a bug where the software was corrupting the show entry, which supposedly was solved.
Try this out, reboot the receiver and when it says 'running self test' hit the 'select' button on the remote or front panel. It should kick into the advanced test menu. Run all the basic tests. In the advanced disk test menu, select the disk you're using (if you have more than one) and run the smart short test and the file system test. It wont take that long to do either. If you have a few hours and wont be recording anything, run the smart long test.
If that comes up good, your receiver hardware and disk are probably good.