After considerable consternation and many system test of memory, graphics card load, CPU load, etc. I decided to check for a new graphics card update. The problem began about two weeks ago, right after I updated to the then most current driver from NVidia. Today I updated to 441.41 (release date 11/26/19) and it solved all of the problems. The prior driver was dated only a few days prior to this new one, so it seems NVidia knew something was wrong and did a quick fix. It would have been nice of them to inform people.