A recently released update for the popular game Call of Duty: Modern Warfare 3 will wipe ALL of your achievements on every single ones of your games. At the time I am writing this, the issue has not been resolved for everyone. Be aware though, all updates for current games will do this.
A mistake in the coding by Microsoft is said to have caused this, and affects most of the players who have updated the game and will wipe all of their achievements. The bug is said to be caused because if you patch any game, it will try and bring your old data from any other XBOX to your current one. The problem is, if you do not have old data, you have nothing to bring over, which results in a blank gamerscore and achievement list.
The support thread for this issue can be found You must login or register to view this content.
So far a common way to fix this issue is to sign out, turn off your XBOX, turn it on again and sign in. If this does not work you will have to re-download your profile. This will bring back any data you lost, but does not include any achievements you earned since the bug appeared. If this does not work, you will have to wait for Microsoft to release a fix.
Stuff like this don't surprise me no more with all the Fucked up people what can;t do there job . It's a multi billion $$$$ company and they can't even get one little thing right, I'm not being a fan as I have both consoles, sure yeah things go wrong, but not little things like this what could of been stopped.