Game files are corrupt, please reinstall.

[Gattsu]

Have done twice and verified the gcf integrity, nothing.

Q9550
HD4870
Windows 7 x64

?

Edit: After playing some company of heroes it now works...

Game seems OK so far.

[twig314159]

Have done twice and verified the gcf integrity, nothing.

Q9550
HD4870
Windows 7 x64

?

Edit: After playing some company of heroes it now works...

Game seems OK so far.

It sounds like your game may have been in a strange state regarding downloading content used by the game. I've seen a few instances where the Steam client will report a game is ready to play but it hasn't actually downloaded all of the content yet. After waiting a few minutes Steam kicked in and downloaded the rest of the content.