@RLGL - thank you for your input on this issue. I did try the repair, but it did not resolve the issue.
@catamountain - thank you for your input on this issue. I never did uninstall anything - MS VC ++ Red’s or my versions of SU, and I’m glad I didn’t. I happened to return here to see if there had been anymore posts on this thread and the other thread. @GTh had posted an update indicating that uninstalling and reinstalling the MS VC ++ Red’s and SU did not fix the problem. Because of this info, I decided to try a restore as you suggested.
All is well in the world - for now. Material thumbs are now visible when I slide the toolbox over to the 2nd monitor. However, as I noted for @GTh on the other thread, I can’t help but wonder how long it will last - when that MS VC ++ Red is updated again, the problem may return.
Anyway… for now, I will mark my thread as solved, but will keep an eye on my versions of SU, the MS VC++ Red’s and @GTh’s thread.