OK. Something is obviously wrong somewhere. Let me know which programmes/channels are affected and I will try to replicate it. All I can say is I'm never asked for a PIN. Maybe there's a fault with your Tivo and your settings are not being remembered.
EDIT: just had an idea. Have you changed your PIN from default 1234? You could try that and then go through the menu again....
Fair enough, you obviously know what you're doing.
I just recorded Messiah tonight [on Drama] and started to watch with no PIN required. I can watch these sorts of prog at any time. Still no PIN If you need a PIN for that or similar progs I suggest you phone it in as a fault. Or is it possibly a channel I never watch? [I think Fox is a known problem, for instance].
One program I know off the top of my head is Ancient Aliens on H2. Always asks for a PIN.
I actually went into a Virgin Media shop in town a few of days to ask how I could get it turned off and the guy in the shop said you can't. He said he lives with his girlfriend and no kids and it drives them nuts too, and he works for Virgin and job is to sign people up. Not a good advertisement.