What's the easiest procedure to resurrect it, anyone?
I tried 'Clear Programme Data & To Do List' first (on Saturday) but the daily call just reloaded the bad slices (because at the time I did not know this was the root cause).
Performing a Guided Setup (on Sunday) brought everything back to goodness!
Except... both my Tivos exhibit the emuproxy-related "failed daily-call" problem (see
http://www.altepg.com/forum/viewtopic.php?f=16&t=1655) which can be worked around by setting the dial-in config code to 126 after each reboot. (There is a permanent way to fix this.) No way to tell if these issues are in any way related, but the short answer is that repeating Guided Setup did the business for me. YMMV!
Many thanks to all those who resolved the issue with the EPG - ourTivos live again!