What happened to the circle around my brush in my spot removal tool?!

I like the spot removal tool. I use it all the time. My son was pleased when he had photos of his teenage acne years and I could remove a blemish.
It's a simple procedure of adjusting the circle size of the spot removal tool to being just slightly larger than the spot you want to move. Simply adjust the circle then click on the spot to be removed.
However, have you ever had the circle disappear and only see an X on the screen?
This can be very annoying since the seeing and adjusting the size of the circle is critical in doing the editing.
Here is an example of the problem. Instead of a circle, all I have is a little cross-hair icon.

 

The problem was, for whatever reason my caps lock key was on. Just turn off the caps lock and the circle needed reappears.

There is another scenario where the missing circle could happen. If my "brush" size in the options panel is too big for my image.

Take a look at the size of my spot healing brush. 

The size of the tool was 800 pixels wide! My photo is only 500 pixels wide. I was lucky enough to see part of the brush helping me to figure out that all I needed to do was reduce the size of the spot healing tool.
No more missing circles!