Spartans! There is currently an issue with the pre-orders of Halo 5: Guardians on the Xbox One that may affect a small number of people who pre-ordered before September 21 and are not using Instant On power mode. Should you be one of these soldiers, you may have an incorrect file for the upcoming game, which will need to be deleted for Halo 5 to be re-installed.
Full story from the WindowsCentral blog...