Gary, thanks. I saw that Microsoft likes to blame anti-virus programs and
Norton in particular. Which I think is unprofessional and rather unhelpful
of them, but I turned off e-mail scanning. That made no difference.
I did come across WMUtil and tried it. Again, no difference.
I had dismissed Windows Live Mail as being an online thing, like Live
Messenger, but ending up trying it anyway. Maybe it would have worked before
the Windows Update, but whatever the Update did, caused the same errors in
Windows Live Mail as in Windows Mail.
But I have seen those sometimes helped some people. So thanks for the
suggestions.
It appears that running sfc.exe somehow solved the problem, though it said
it found corrupted files that it couldn't fix. The log file is so HUGE that
there is just no way I can check out which ones it didn't fix and even if I
found them I wouldn't know how to fix them. But it seems to have fixed
something, even though the Microsoft documentation says the messages that it
has fixed a file are misleading. (Very strange!)
Then I was finally able to get back into Windows Mail. Importing the mail
files from a backup worked, though it wanted to keep re-importing them, so I
have some duplicate folders and folders misplaced, but we can now get at the
messages. Hurrah!
Thanks again, though, for the suggestions.