No.

Task Manger does do more than briefly show the hourglass, though. It goes to a black screen of death, then after another five or 10 minutes the regular desktop comes back with all the QuickLaunch icons. Sometimes the applications will then run, sometimes I have to wait a bit longer.

Windows File Explorer will always run immediately on bootup or at any time during the five to ten minute wait -- but it only shows a blank screen, no data within the window, and shortly thereafter locks up with a "Not Responding" error. If I try to close the window, I get black screen of death. No matter what happens, if I wait long enough (5--10 minutes), suddenly everything will return to normal and the computer runs perfectly after that.

I believe this behavior began the first time I booted up after the Windows 10 update referenced above. I could be mistaken, I might have gotten one or two problem-free boots after that, don't know for sure. And I don't know if it is only a power-off reboot that causes it, or if a restart would cause the same behavior. When I know it will be five or ten minutes of downtime every time, I'm reluctant to experiment.

I haven't tried booting up in Safe mode. That will be the next thing to try, I guess. No, the next thing I will do is a full system backup right now while the computer is still working!

tanstaafl.