Unsure that this is the problem, but steam consistently tells me that one file is not good when I check the game integrity.
After it updates, the game is OK (consistent.)
When I lauch the game, it first sync with the steam. Then it fails.
If I go check again: the game is again unconsistent, with one file not good.
So, what's this problem, and how to I solve it ? Looks like a steam problem there...