I was reading about Halo 2 where someone from Bungie explained the pop-up during the cutscenes. Supposedly the flickering/pop-up is because Halo 2 uses the in-game engine to create the cutscenes, rather than pre-rendered ones. Apparently they made this decision because pre-rendered cutscenes would require loading screens, which they said they felt would "detach the player from the flow of the game". And pop-up doesn't???