Nice solution. Just found this thread. I remember wrestling with this problem about a year ago and could never find a solution. I'd log onto my computer only to find a giant rifle pointing straight at my face every single time for some shoot-em-up game. Disturbing! No wonder why the world is so F'd up.
Then I just thought to press the escape key before logging in and all my troubles went away. What I noticed is that they strategically placed the ad prompt over the login pad, so turns out by pressing the escape key, it clears the ad away from hijacking your login before you can unknowingly click it, and whala you're in!
It's sad that a thread (a long thread at that with no response that I've notice from a Microsoft rep) even has to exist. It just shows how low big tech will go to screw their own customers just to make a quick buck.