Oh well, that is a good result.
Just deleting the thumbnails databases may have also worked, as that seemed to be where the problem was, and an uninstall would remove them, while a reinstall would rebuild them. But no matter, it's working again. 
PS: Get that sword mounted on a wall. It should be seen, and be a reminder to maintain honor, and of how fragile life is! 
One last thing...
When you said to delete the thumbnail databases, I deleted everything that was in C:\Users\ALB\AppData\Roaming\J River\Media Center 25\Thumbnails on the Client machine. I then rebooted and restarted that Client and after it finished populating everything with a Thumbnail, I still had the problem. At that point, I said to myself, "
Should I have done this to the Server too? Is something borked on the Server-side that messes up the sharing with the single Client?" Rather than making any additional attempts to
fix the problem, at that point, I thought it's not
that much work to uninstall and reinstall on both sides. Before I got off the computer for the night, I performed that action so I didn't have to watch the entire rebuilding processes.
I wanted to say the above because I don't want you to think I blew off your advice to fix the problem. I did try. Again, I'm extremely thankful for your help & suggestions.
