J'ai trouvé ça en cherchant sur les réseaux anglophone
This is a common problem and has been discussed at length. I am sure you can find topics on the next few pages but I will tell you how I fixed it.....well %95 fixed it.
This only works for Windows 7 so if you are using something else please scoll on to find another topic of this nature.
Do a search for AssassinsCreedIIgame.exe. If you are using steam you can find it here:
C:\Program Files (x86)\Steam\steamapps\common\assassin's creed 2
Find the compatibility tab. Set it to run under Windows XP Serive Pak 2. I never tried the service pak 3 option so it probably works too.
Restart the game. Win7 will ask you if you want to continue with the program. Say yes.
I started where I left off with my last data loss. Only 5 missions into the game. I made it to the end of the game with only 2 save games lost and I saw it happen as the saving 'diamond' was stuck on in the lower right of the screen. I went from constantly losing data to it only happening twice.
En gros il dit qu'il faut que tu mette Assassin'screedII.exe en XP service 2 que tu lance le jeux, il vont te demander si tu veut continuer avec ce programme et tu répond oui !