odd display problem

[Richard in Idaho]

I had a program that was not responding.
So I did a Ctrl-Alt-Del
When I hit Del the display rotated 180 degrees left to right.
The top of the display is now on the bottom and the right side is on the left.
Makes the mouse hard to use.
A reboot did not help and I cam not log in. Password does not work.

I replace the monitor with an old one that I was not using. It is working just fime.

Any ideas as to what happened?

Thanks