Why does my mouse turn into a single pixel, and how can I make it stop that?

[Guest tim conway]

I have to tap repeatedly on control and scan my screens for the little contracting circle and center that over what I'm trying to click. If it's on a flat white background, I can see the dot, but in most things, particularly skype, with its black background, all I've got is the rings. It's difficult to even get on the X to close something. It works for a while after reboot, but then, a little later, it t's back to the dot. I've tried setting up a big bright orange cursor, but it's like that only in places where windows changes it, to the text entry or finger cursor. No big orange arrow as

 

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