I get a different error from time to time: Campaigns - Error: System error. Please contact MSN Customer Support and refer to this error number: 1.
I contacted Customer Support and they said: MSN adCenter is currently unavailable due to undergoing maintenance. Although adCenter is going through some updates, all ads are running as usual. We sincerely apologize for this inconvenience.
SO I get an error, just a different one than you. It would seem better for them to state it was undergoing maintenance (as Google and Yahoo do) rather than submit the error message.