Sometimes the HD Data is corrupted for whatever reason. To fix, just head into your Hard Drive by going to Settings > System > Storage > Hard Drive.
Once here, select Games and Apps > Halo 4. Scroll down to "Spartan Ops Season 1.0" and Select it. Delete it.
After all this, Insert Disc 2 of Halo 4 and reinstall the data. If you have any more problems, just let me know and I'll try to work it out with you.