Never mind. Whatever caused it stopped. Go figure...
When possible I do, and in this instance I did so without any change with the problem. The next day, it just started working and has been ever since.
This server has other solutions shared on it, so a reboot has to be scheduled in advance. That tends to slow problem solving.
I still have no explanation for what happened.
Voodoo or Smoke & Mirrors. Likely it will never rear it's ugly head again.
Ok, I was just curious. Thanks.