We now know what causes the 400 vs 600 hour issue, but we have not heard of the problem that you are experiencing. I doubt it's related to the capacity.

Given the symptoms, it's hard to know what the cause is without actually seeing the unit, unfortunately.

I figured it out: I switched external drives. -->idiot<-- I unplugged stuff during the hurricane, and obviously didn't pay attention to what belonged where. Part of the reason I thought everything was ok is both TiVo's booted up without a hiccup. It was only when I tried playing some stuff on the other TiVo and getting "this program has no video signal" that a light bulb flickered on in my brain.

(I was always under the assumption that TiVo's with wrong external drives would scream alarms and warnings--or at least fail to boot. One of your tech support guys said so himself unequivocally. If only I had tried testing some recorded programs, or better labeled my eSATA cables....)

The other TiVo is fine after switching it back; apparently its external drive wasn't touched by the "blank screen" TiVo during the switch. Time will tell if this is actually true.

The correct external drive for the "blank screen" TiVo is probably ok too, since the other TiVo just sat there, unmodified and not recording anything. (It had no cable input either.) However, I believe either the Guided Setup redo or any recordings (live and/or scheduled) obviously did in at least its internal drive: It blank-screens with its now-correct external plugged in, too.

I'm not betting my life that the recordings are salvageable, but when you get the unit, try to see if something's recoverable if you're able. Thanks.

By the way, just out of curiosity, exactly what was behind early 4TB units stopping at 400 hours? And would sending in my working 400 TiVo to fix it to 600 hours result in keeping, or the loss of its recordings?

The problem was attributable to a bug in the software that we developed to create the 4TB system. Unfortunately, to get the full capacity, we have to reload the drives.

Final question: are the 400's stable enough to leave be? Thanks.

To the best of our knowledge, yes. But the handful of customers impacted have had their units reloaded.

Amazing but true: For the lack of anything better to do, I left the blanking-out unit plugged in (and connected to the correct external drive) over the Labor Day weekend. When I returned this evening ... the unit was chugging along, as if nothing happened.

After all the hoopla died down, three things come to mind:

A) Contrary to what one would think, TiVo's do boot up with the wrong external drive. Not a good thing.

B) For some reason, however, TiVo's may know something's wrong and, instead of plowing through and wreaking hard drive havoc on an incorrect external drive, somehow "shut down" (hence the blank screen) while at the same time trying desperately to reconnect to its original external drive once the correct one is actually connected.

C) It's vitally important to label one's eSATA cables exceedingly accurately.

Anyway, just thought you guys might want to know.