It's called a
broadcast flag.
http://en.wikipedia.org/wiki/Broadcast_flagTV companies started tinkering with this a few years ago, but I didn't think that it was actually operational yet due to the controversy surrounding it.
The point is exactly as you've discovered, to limit the recording of certain material. The last I've read about is that it's sort of in limbo, and that neither Tivo nor other DVR's pay attention to the flag yet, or that cable/satellite companies weren't broadcasting it.
However, it seems that you've discovered that your cable company and/or Vista might just be using it. You're the first person I've ever run into that's actually experienced content being locked down by this flag.
It's possible that it's a bug too. Is the first time recording the show? I know I remember reading about a similar incident on a Tivo forum once, and the cause was traced to be a mistake by a broadcaster. Or perhaps it was a Tivo software bug. Either way, the problem was just an error on someone's part and was quickly corrected.
My only advice would be to ask the great Google and see if you can find others complaining about it. If it's a legit block, I'd bet you can find a forum where it's being discussed.
