Just now, though, I needed to edit the file so a PDF wouldn't work, and I got a little frustrated, so I tried re-opening it several times in annoyance. And each time it barely started loading the file and then crashed.
And then something interesting happened. A dialog box came up saying, "It looks like Office is crashing repeatedly. Would you like to run Office Diagnostics?" So, I clicked "yes", and it did a bit of checking, and it eventually reported that there were some setup errors, and it had fixed them. (It also reported that there was a RAM error, but the help on that suggested that if there were also other errors that had been fixed, I should re-run the tests to see if it went away -- which seemed a bit odd, but they did indeed go away when I re-ran them.)
After that, it seems to be working fine.
I have to say I'm impressed. Problems like this will show up in software this complicated , but this seems to be a fairly effective way of dealing with it -- and I didn't even have to go looking for it; it was just there when I needed it.
So, I highly recommend the Office Diagnostics thingy, if your Office install is acting weird -- it's in the programs menu under "Microsoft Office Tools".
 "UNIX systems generally have a good, though not impeccable, record for software reliability. The typical period between software crashes (depending somewhat on how much tinkering with the system has been going on recently) is well over a fortnight of continuous operation." --Dennis M. Ritchie, 1978
Crossposted from Dreamwidth (original here), with comments. Comment here or there.