I've been using Mac OS X for maybe 6 years now, and I have no idea what's causing this. Maybe someone else has this experience and can help me out.
Symptom: while holding the alt/option key, if I move my mouse the current window starts resizing, anchored at the top left (it behaves exactly as if I had clicked-and-dragged the lower-right icon on the window).
Anyone have an idea of what I may have installed that caused this? Or how to make it stop?