I'm playing through the game and had just got to the point where master chief jumps through the porthole that Cortana opens and....i get the Halo 4 start screen again telling me to press start? i go to campaigns ,select the missions i have played and try to start Forerunner,it says it's preparing the game...loading etc..etc but seems to fail and after several attempts to load i get the "one player may be missing downloadable content"?? whats going on? do i need to load the second disc for campaign as well oor just multiplayer?