I couldn't think of a better title, that's basically it.
I boot up, OS starts up I log in. If I immediately go to sys prefs > Displays ... I can see a smaller 3rd monitor in "arrangement" ... after a few seconds...both screens turn blue (as it does when it's changing monitor layout. Then comes back only showing the 2 correct monitors. Does it every time. Nothing else is attached. It's an older 2008 MacPro with a KONA LHe card.