That sounds like a problem with your videocard. Try to get the latest beta drivers.
If that doesn't help, I guess it could be a bug with your particular hardware configuration? Check the Steam forum if it ever comes back.
edit: Oh wait, incorrect textures are appearing? You can try validating your game files by right-clicking the game in Steam > Properties > Local Files
If that doesn't help, I guess it could be a bug with your particular hardware configuration? Check the Steam forum if it ever comes back.
edit: Oh wait, incorrect textures are appearing? You can try validating your game files by right-clicking the game in Steam > Properties > Local Files