Just lately, if I have two windows or more open in an application and I move the mouse to the top right of my screen, all but one window disappear, shooting off to the side or bottom of the screen. If I close that window, another slides into place. Occasionally I can reverse the condition by moving the mouse to the top left, but only sometimes. I do not have "Hot Corners" enabled for anything as I think they're bloody stupid, and I do a lot of stuff in Illustrator, so I'm often poking around at the edges of the screen to drag stuff around. WTF is going on?