After going through the endless loop* of Win 8.1 updates one more time (2-3 more times?), I again used the 3-finger salute to finally bring my system to a halt. I rebooted and got the lockscreen and logon screens as usual. I then went to Settings \ Control Panel \ Troubleshooting \ Fix problems with Windows Update. All now seems well, I no longer have notification of impending (possibly installed but unrecognized) updates, and the system seems operating just fine. Too bad Microsoft makes one jump through so many hoops to fix a problem caused (apparently) by their own code.

*Updates download & process, "install" but install fails, undo changes, revert to previous configuration & immediately launch new round of process, fail, undo, revert, . . . . .