I rented COD4 for the first time

[Indifferent Clox]

I really never was big into first person shooters untill this year, I loved deus ex and a few others but mostly not my thing untill recently.

So i rented COD 4 which by all means should be an amazing game but then something fucking weird happens

The guys mouths are moving, and by all means they should be talking, and every once in a while if I restart they might, but either there dialogue will happen 30 seconds after it is supposed to or not at all. This wouldn't matter if it didn't flesh out the story and add a major element to the game.

Did anyone else have this problem and could it even be a disc cleaning problem or is it just a faulty version of the game?