If you notice certain apps not loading like Mail, Calendar, and Contacts, it might be because of a problem with the Windows Live login system. In Windows 8, you can log into your PC using your Windows Live ID, which they really want you to do or login using a local ID like you have in all previous versions of Windows.
Obviously, anything new is going to have bugs and this is one of those new frtures. Go to the Metro UI Settings and then click on Users. If you don’t know how to get to Metro UI settings as opposed to Windows settings, don’t worry, you’re not the only one. Read my previous post on how there are two sets of settings in Windows 8, one for Metro and one for Windows.
Go ahead and click on the Switch to local account button. Now go ahead and try to open the Mail, Calendar or Contacts app and see if you can get in. If so, it’s a problem with the Live ID system and you may have to try it again later on. You’ll see the option change to Switch to Microsoft Account.
"Windows 8 Tips-- Windows 8 Metro Apps,Log in Using Local Account"
Reference : online-tech-tips.com