We are aware that some of you may be experiencing difficulty accessing your Windows Live Hotmail accounts. We’re actively investigating the cause and are working to fix this as quickly as possible. We sincerely apologize for any inconvenience and disruption this may be causing you.
The Windows Live Hotmail Team
Update: Service has been restored for all users, and we’re taking steps to make sure this doesn’t happen again. Thanks again for your patience, and we’ll make sure to keep you updated.
Hotmail team blog archive 