Like many others here I am suddenly unable to send or receive from my default msn.com account in Windows Live Mail running under Windows 7, receiving the above message when I attempt to do so.  I have tried:

1. Removing and adding back the acount
2. Uninstalling Windows Live Mail, deleting all associated registry entries, reinstalling Windows Live Mail
3. Opening a new Outlook account, logging in with that, logging out, trying original account again
4. Following the "Resolve Machine Reconfiguration Issues" steps ( REGSVR32 initpki.dll is missing on my computer)
5. Turning off firewall

None of these make any difference.  The account is still accessible on the Outlook website, and my other msn.com address still works in Windows Live Mail.  Any help fixing this would be greatly appreciated.