I posted this earlier today, but it didn't go where I intended (the Bug Reports subforum), the post got generally screwed up, and I'm not sure if it was seen, so I'm trying again.
When playing the game in full-screen mode on a multimonitor system the mouse cursor is not "locked" within the game. That is, you can move it outside the gameplay area on one monitor on to your computer desktop on the other monitor. If you move the mouse back into the game, you're fine, but if you click outside the game, the game gets minimized with an effect similar to ALT-TABing.