On mine, Windows update plus Steam update plus forgotten password = I can't get mine going yet...
Mind you now, mine is a Steam version, which is a bother of course, and it's been over six months since I noodled around in it, but mine won't start either - but it's because it's back to the state it was in the day I bought it. All that trouble I went through with the Steam tweaks here, and they're gone. I have to go through the "authentication procedure" again... Whether it was a Windows Update or a Steam Update, dunno. Might have just been from not logging into Steam for a while. Stinkie.