I saw before I was not the only one to experience it, but none of the solution proposed works. My problem is very simple : Portal 2 launches alright, but whenever I try starting a game, at the end of the loading screen, it simply crashes.
If I check the files, it says one of them is broken and will be downloaded again.Then it's OK if I check the integrity again, and when I start a new game, it crashes at the loading screen again. One more thing : when I launch the game after the files integrity is OK, it says something like "finalizing installation".
This game has been out for a while now, I bought it FULL PRICE and couldn't play it before. Is there a solution or did I waste my money ?????? (or will Valve give me my money back ?)