Well, this is rare. The 360 and PS3 versions of EA's sci-fi survival horror game Dead Space will be arriving in stores earlier than you thought. I'm not sure how exactly this happened, but the explanation probably involves a virgin sacrifice or two.
Update: I've had a couple people tell me that the October 21st release date for North America had been announced a month ago at E3 and that only the European release date was changed today. Consider the North American release date confirmed, then, rather than changed. To be fair, the trailer at E3 (posted at the bottom of the story now) lists the release as "Halloween 2008" so the confusion is plausible.