I'd try restarting the computer first.
I did try that….in fact twice.
It has happened before and unknowing as to what I did, it stopped. Today I can’t seem to get that same result.
I found out the problem. It was a mouse malfunction that only reacted to my InDesign files. When I switched out the mouse, the problem went away.
Thanks for your suggestion though to restart. That quite often works.
Problem SOLVED. It was a mouse malfunction reacting only to my InDesign files. After switching out the mouse, the problem went away.