I <3 Halo:Reach - amazingly fun and best campaign + amazing Soundtrack
I <3 Halo 3:ODST - best soundtrack + Firefight + Coastal Highway and Mombassa Streets, amazingly unique campaign.
I <3 Halo 3 - best multiplayer levels + Forge + best Custom Games + soundtrack
I <3 Halo 2 - amazing huge fun campaign + soundtrack + Fun multiplayer
I <3 Halo: CE - started it all
Posted by: TheSpiderChief
It's a common glitch. It's happened to everybody at least once since Halo: Reach's release (3 times for me).
And, yes, you have to do it on Legendary again. But only if you want too. Personally I couldn't give a damn about completing it again on Legendary. I have the achievements to prove I've done it.
Hasnt happened to me.
Want to know why? It only occurs if you shut of your xbox while in the middle of a campaign game, or while you shut it off while the game is saving.