When trying to play any of the DLC maps in customs or forge, it says "Player failed to load content". I purchased both map packs, and it still wont let me play them. Ideas?
You could try deleting them off your HDD and re-downloading them, I think that's how it was fixed in Halo 3.
If you delete the DLC after purchasing it, you can download it without having to pay more Microsoft points. Try removing the packs from your HDD and then re-downloading them.
No, they did, I was in a lobby with Rorak, Shad0w, etc. and we were testing some of the Hub Of The Dead Submissions. When they put on Parallex (which is on Tempest) It said "Player failed to load content" and my name was blinking. I left and went into forge, and I couldn't play any of the DLC maps. I'm probably gonna go ahead and do what Pino and Chron Suggest.