cna't play halo 4 campaign past the intro vid

[Chris John Willett]

so i decided recently to do a legendary run of the halo 4 campaign as i was getting bored of play non-stop halo 4 multiplayer but it jumps me back to the menu when the intro cutscene is finished. i tried loading the first level manually but it says i don't have the required download or something like that. i have completed the campaign multiple times,i treid backing up the disk to my hardrive but it stoped, i have an xbox 360S, i have tried turning it off and on again, the disc has hardly any scratch but i cleaned it anyway, the second disc has been downloaded and i put that disc back in anyway. i just don't get it, campaign worked perfectly fine now suddenly it does not work? and i really don't want to start everything all over again, i have played too much multiplayer to start over