Thanks, @RJanata for this info! Installing Dropbox desktop version 112 worked for me, too. I could not find release notes for Dropbox's desktop version 112. But, the Dropbox users in the Dropbox forum that Rjanata linked to (in quote above) believed that it was the install of Dropbox v111 that was the cause. FYI-I'm running Eset 18.104.22.168 and Win10 x64 and had just completed Microsoft Win10 update KB4592428 the night before I had the problem. So thought it might be an Microsoft interaction. But, from looking at the Dropbox forum, it appears that the Dropbox version 111 was the problem.