There hasn't been a software update for series 1 units, has there? That was actually my first (well, second; rebooting it was the first) thought, I even went so far as to dig through the menus to see the software version, but there was no clue as to revision date, so that proved fruitless.
However, I did make an enlightening discovery.
The remote has a very sharp threshold for battery voltage. When voltage drops below about 1.2 volts (for each battery) then apparently it stops sending repeat signals when you poress and hold a button.
A pair of new batteries (~1.6 volts each) restored full functionality to my TiVo.
It looks like there is considerable current draw on those batteries -- putting my meter across one of the batteries would show a voltage drop from 1.6 volts down to 1.4 volts as long as I held a button down, and the old batteries would drop from 1.2 volts down to about 1.1.
Hmm... maybe if I put some 3 volt lithium batteries in place of the 1.5 volt alkalines, I'd
really speed up my UI...
tanstaafl.