I can't imagine I'll find an answer to this, but at this point it's more of a curiosity question than anything else.
I've owned about eight Tivos, and I've had them apart practically down to the molecular level. My mom now has my old S2, and she's on RCN and is using an older cable box (DCT2500 I think) with a serial cable to change channels. It has worked like a champ.
She started to mention that some recordings were freezing - the video got stuck on the screen but the audio would continue, and sometimes it would come back after a few minutes. Other times it would continue to the end of the recording.
I know, I know... Failing hard drive, right? Or flaky power supply. Please stay with me for a moment.
I figured I'd get around to looking at it eventually, but in the meantime she acquired a hand-me-down Humax with a DVD recorder. Nice. She then had both Tivos hooked up in separate rooms, both on DCT2500s.
So as a fail safe, if she was recording something she really didn't want to miss she would schedule the same recording on BOTH Tivos instead of just the failing one.
So guess what? We discovered that when the recordings are hanging, BOTH TIVOS ARE DOING IT AT THE SAME TIME! She had a bad recording, decided to watch it on the Humax, and it had hung at the same point. She's been able to confirm multiple instances of this happening over the past few months. I also had her transfer a bad recording to her PC with Tivo Desktop, and it hangs at the same place when watching it there too.
So I'm really stumped. Can't be failing units, it must be something in the signal that is causing this to happen. She has never observed this on live TV through Tivo, though it could just be by chance, nor has she seen it on a third TV with no Tivo, just a cable box (not a 2500).
The only even vaguely similar case I could find on the net was just one Tivo and it was a bad signal splitter. I guess not many folks have two units connected the same way!
I welcome any ideas, though I'm really not expecting a fix at this point. It's more of a technological curiosity for me. Thanks!