[RightWhale]

If you can use your mouse to catch a popup that won't die, you can sometimes minimize it on your Windows screen. This way it is there and happy to be there, but it is out of the way and works for you to intercept other popups.

[Lazamataz]

ALT-F4 works wonders for when the popup is coming up but is not yet formed enough to have 'deactivation' code.

[billybudd]

Hahahaha! I love your comment!