I am also similar problem from today as i am using window live mail with two gmail accounts and one hotmail account, both gmail account has no issue but while loading hotmail account mails i get below message, please confirm the solution ASAP.

Unable to send or receive messages for the Hotmail account. Header download for the 'Inbox' folder did not complete. Could not update cached message flags with IMAP server.

Server Response: The server did not respond to this IMAP command before the connection was terminated.
Server: 'imap-mail.outlook.com'
Windows Live Mail Error ID: 0x800CCC0F
Protocol: IMAP
Port: 993
Secure(SSL): Yes