Thank you to all who provided suggestions. I ultimately concluded that I was going to have to do a clean install of Windows. I did that and it worked! Now for the long task of reinstalling...

ELPUSHER - Thanks. I will check that out now. I assumed that when I flashed the BIOS, I had the total package, but that may have been a mistake. I also plan to again try using msconfig to boot...

pparks - Thank you. I will probably have to reinstall, as you suggested. Needless to say I am putting that off until last, since I fear that something will go wrong. I suppose I shouldn't worry,...

Berton - I booted my Ryzen 9 twice from Mint live sources (DVD, then USB). It was difficult to test for the problem, since I could not add software that was not already there. I didn't find any...

Berton - I have Linux Mint installed on another desktop, but I am unsure how you go about making the copy you suggested. I assume you mean to create a copy of the Ryzen Windows install and boot from...

joeandmargo: I have gone through all of the items. Reliability Monitor didn't show anything special. A few random "software not responding" errors were present. It did give a large number of "not...

I have run out of ideas--my Ryzen 9 build (mobo is MSIMEG x570 Ace) is sort of working, but has keyboard delay (I can type 8 - 10 characters before they appear on the screen) is sometimes in seconds....