Today (10-12-10) I was playing Halo: Reach and working on the daily challenges. While playing the campaign, I died and it said that I failed the challenge "Return Of The Mack". The description of the challenge is Kill 50 Elites in Campaign today on Normal or harder. After it says that I failed it, I had to exit campaign and start a new level in order to have access to the challenge again. This is the first time that I have ever failed a challenge on Halo: Reach, and I'm not quite sure why. Has this happened to anyone else or does anyone know why this would have happened?