Ubisoft has released a patch updating Assassin's Creed to v1.02. See the changelog below.
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Assassin's Creed v1.02 Update
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* Fixed a rare crash while riding the horse in Kingdom
* Fixed a corruption of Altair’s robe on certain graphics hardware
* Cursor is now centered when accessing the Map
* Fixed a few problems with Alt-Tab
* Fixed a graphical bug in the final fight
* Fixed a few graphical problems with dead bodies
* Fixed pixellation with post-FX enabled on certain graphics hardware
* Fixed a small bug in the DNA Menu that would cause the image to disappear if the arrow was clicked rapidly
* Fixed some graphical corruption in Present Room with low Level Of Detail
* Character input is now cancelled if the controller is unplugged while moving
* Added support for x64 versions of Windows
* Fixed broken post-effects on DirectX 10.1 enabled cards
