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My xbox 360 was sent in for repair and I got it back yesterday after 5 weeks. I update everything, redownload the maps twice, delete them off hard drive and download them again, and I cant get into matchmaking.
i got a flaming helmet from Lukems girlfriend one time and i couldn't walk right for a week.
You need to reset your 360 to default first. I believe you can do this on the last page of the setup screens.