Thanks--that's the culprit all right. However, the auto-fix said "failed to correct" or similar. I'll run thru the manual fix and see if that does it.
As an aside, I use Firefox as my default browser, and I see the Microsoft fix is geared to making IE the default. That strikes me as a likely snafu.
But again, your brain saved me quite a few hours of search time, so many thanks!