Contacted TiVo support - they didn't have a clue and are going to switch my unit.
Of course, that means two to four weeks of no TV, let alone TiVo.
For something I paid $1000 for less than six months ago, I'm very disappointed. It took me over a month and a half to deal with Comcast to get cable cards, then another month of the SA cable card problem until TiVo silently sorted the problem out (and didn't bother telling anyone they'd fixed it, at least work-around wise).
So, only two months of seamless usage on the box and it's gone to crap again.
It seems to freeze the most, once I get it running with some semblence, on high-def channels. But it runs slowly through menus if I manage to TiVo Central past the boot-up THX screen in time.
I have to assume there is a poor hard drive usage/compression/cleanup going on and after all the usage, it's just a fragmented mess.
Of course, it'd be nice if TiVo would look into the many people having somewhat related problems and actually update us on what is going on, but my past experience (the SA card issue) shows that they just tend to ignore, deflect and plow ahead without caring about us, the customers who have been their marketing department since the beginning.
I may change from a TiVo advocate to my friends and coworkers to someone who warns them to avoid it at all costs, to the tune of my $1000 mistake.