Assasins creed 2 xbox is broken, patch inbound

Word spread over the weekend of a serious glitch in the Xbox 360
version of Assassin's Creed II that requires players to start over from
the beginning should they encounter it, a not negligible concern for a
game that clocks in at between 20-30 hours. The bug arises when players
quit the game immediately following completion of chapter 11, before
leaving the hideout. Should a player exit the game at that point, upon
resuming their game, they'll essentially be stuck in the hideout with
no way out.

Ubisoft announced that a patch will release soon to fix the issue, but a date has not yet been specified.