xInFeRnO Funny, this often pops up when hackers have published your password on the open web, and Microsoft has locked your account until you can confirm the details. Here's a way to do that:
0) Since these web pages are .ASPX pages, this is best done with Internet Explorer. If you don't have IE, Safari or Firefox are better than Chrome.
1) Go to http://account.live.com and sign in there with the Microsoft ID (formerly the Windows Live ID), the email address used to create your XBL account. If you see any message there about a blocked account, follow the instructions precisely.
2) Click on Edit Security Info to replace your Microsoft ID security data , adding 'proofs', security data needed to recover your account and verify your identity.
3) Sign out, go back to http://account.live.com and sign in there with the new Microsoft ID.
4) Go to Xbox.com and sign in there, too. If you see any message there about a blocked account, follow the instructions precisely.