Thank you for the reply! I didn't have the time to wait for it, though, as I need my computer for work, and I needed to solve these problems immediately. I manually reassociated all shortcuts and filetypes. It added half a day to my being unable to work due to the update, but I guess if I had waited for these suggestions it would have been at least two and a half days killed by the update.
I will hold onto these instructions in case future updates also kill shortcuts and associations.
Clearly a failure to update was not the problem, but I suppose you deal with all these issues with a cut and paste.
Thanks for the response. Perhaps it will be helpful in the future.
Of course, it would be better if updates did not corrupt system files or do things that result in broken associations. It's unlikely that I started with corrupt files, because other issues have required me to run sfscan and dism scan recently - suggested by MS as a way to solve a problem I was having where Windows Explorer quit a few times an hour. (The scans did not help, but turning off Windows Error reporting, at least the part that sends MS information, ended the problem.)