Okay, sorry for all the questions.
There are many people here with your same hardware. I seem to remember something about a setting in the Nvidia app causing a problem like this, but I don't remember exactly what it was. This sounds very familiar to me...
Adding a screenshot to make it easier to show to others:
This looks so familiar, I think there's a setting in the Nvidia control panel that will cause this, but I can't remember.
For all those settings in the Nvidia control panel, you usually want them set to "application-controlled" or "use the 3D application setting". Maybe some anti-alias override is causing this?