I bought the game through the Green Light bundle, downloaded it and got the exact same issue; asked for the cd-key every time, then the game crashes with the same DOFupdater.exe error. Windows 8 x64 bit.
I have to say, coming here and finding a reply of "oops we don't know, guess you're out of luck" is truly baffling and concerns me greatly as a new customer. Offering a refund is one thing, but given that I found out about this game in the first place through a promotion to get it on Steam it doesn't exactly bode well for me.
Very hopeful you guys can come up with an actual solution instead of expecting people to shrug.