It is frustrating when the mouse you are using in Microsoft Windows 10 “magically” transforms from a pointer into a fuzzy looking square.
It looks like this:
I have not figured out why this happens on my dual display setup. It could be a graphics card / USB VGA adapter driver issue on Windows 10, or an LED monitor fault.
Previously, I used to restart my system, however I have found a simpler solution.
Now, I just toggle the Enable pointer shadow check box ON or OFF in the Mouse Properties in Control Panel