Technical Problems Present in Halo: Reach Defiant Map Pack
Having trouble playing the recently released Halo: Reach Defiant map pack? You're not alone. A bizarre tech issue has reared its head. The problem is linked with the number of Marketplace Content items you can have active for Halo: Reach at any one given time (currently, three content items). So if you're breaching that limit with exclusive armor, Bungie Pro, or other map packs, the Defiant pack won't function correctly.
The bad thing is, there's no long-term solution as of now. But you can head to your Xbox 360 console's memory menu and delete items to free up space. Bungie has made clear that deleting your Bungie Pro confirmation item will not affect your Bungie Pro membership, so that's the best option unless you really dislike your armor. Besides, everything can be re-downloaded at no extra cost, so making a sacrifice for a couple of days isn't too much of a worry.
There's another issue surrounding the pack's single Firefight map, Unearthed. A "players failed to load content" message has been spotted on several occasions when the map is selected from within the lobby. This is a storage issue specifically with memory cards, and can be solved by downloading the DLC to the 360's hard drive and using that to run the pack.
The Bungie blog has an FAQ available and updated regularly should you be stumped with any other problems. The studio has been in direct contact with Microsoft and 343 Industries, so expect a permanent solution within the coming days.