THANKS. The suggestion to check out the "preferences" was the key. The last Lightroom upgrade to version 7.4 seemed to have reset all my preferences back to what I call Adobe preferences. The only reset that had come to my attention since installing 7.4 was the one that caused the attempt to auto download. But on careful review of ALL preferences I found many of MY PREFERENCES changed in 7.4 upgrade to what I call ADOBE PREFERENCES. And since Adobe and I seldom agree on how to manage my files I basically reset almost every option to return it to the way I had it before 7.4 upgrade.
Thanks ADOBE for the sabotage without warning!!!!
Answer found, good.
Apparently one (or more) of your "MULTIPLE READERS" was being detected as "Removable media" (as are Camera Cards).
It is not only Camera Cards that can trigger the Import dialog, but many things "Removable".
I cannot explain the Preferences reset. Normally that would not occur with an update. (never has for me- thankfully)