I can’t understand why all my achievements earned playing Halo Reach would be completely wiped out. After I down loaded the new updates from XBox Live and went into Waypoint everything was gone.
I contacted the people at support with XBox. They had me delete my profile and put it back in to see if Waypoint would pick up the information again. It would not!! Why tie certain pieces of armor, ( that can only be obtained through Waypoint ) for the game to a source that looses the progress needed to get the armor.
It is very frustrating to have everything wiped out!!!
The Halo Waypoint forum team is aware of the issue and is working to resolve it. All we can do now is wait! If you legitimately earned the achievements, they haven’t been deleted. You can even go to xbox.com and view them there. 
Dont worry , you have not lost any of your achievements, halo waypoint is simply experiencing some technical problems with some some updates that have to do with halo 4. Its been like this for at leas the last 7 days. The will be fixing it soon dont worry.
Thank god man. I was looking this up because everyday I log into Waypoint I go down in my career. From 39 to 31 (There goes my ODST achievements) now it’s at 24 (There goes my Halo 3 achievements), and now it’s at 1 (there goes every achievement I ever earned) Look mom I’m a noob again. I really hope they get this fixed. It’s super annoying not to have the armor unlocked in game but not for waypoint to register it.