So I just started up the game after installing it and after watching trough the intro and selecting my character ( Carnby of course). The problem is that I am able to walk trough everything and the screen doesn't change, for example I can walk trough the rocks in the first scene and way out of the screen but nothing happens.
Anyone else got the same problem and more importantly a fix?

I actually got this on the first screen as well, but as soon as I walked off the bottom of the screen into the next scene the problem never appeared again, try restarting the game and see if the problem corrects itself when you leave the scene of the parachute hanging from the tree.