Hmm.. I thought there's a way to download achievements from the net and transfer it to your hdd? (in other words, cheating)

In the Spring Update, Microsoft has implemented a new protection against gamesaving by using our gamesave archive against us - they went through our gamesave archive and downloaded all the saves, then everyone who has uploaded saves in the past has had their current local "ConsoleID" values added to a Console Revocation List implemented in the new spring update.

Decrypted Console Revocation List
Any gamesave coming from these ConsoleID values is now recognized as corrupt in the latest update. Which means if your on the list, saves created on your console will now only work on your console. Your transfer privledges have been revoked.

If you are (or were) a member of 360gamesaves and uploaded any gamesaves, please check the forums for more information on determining if your ConsoleID has been "revoked". If your ConsoleID is not in the list but you have uploaded a gamesave recently and wish it to be removed from the site please PM a forum admin.