The Ctrl-Alt-Direction key sequence is supposed to be used for changing your workspace. On my computer at work it changes the screen orientation.
Ctrl-Alt-Up – right side up
Ctrl-Alt-Right – 90 degrees
Ctrl-Alt-Down – 180 degrees
Ctrl-Alt-Left – 270 degrees
Not that I would, but people who leave their computer’s unattended need to have this happen to them. Often.