iCal server busy or unavailable

For sometime now whenever the iCal on my mac (Version 5.0.3 (1605.4) attempts to synchronise itself with iCloud I get this very annoying message-

"The Server is Busy or Unavailable.

The server at cal.me.com is currently unable to handle the connection for account “........@mac.com” due to a temporary overloading or maintenance of the server. If this continues you should contact the server administrator.

You may try to connect to the server again or take the account offline."

The options of 'go offline' and 'try again' both produce a repeat of the message a few minutes later.

Strangely, when I then looked at iCal in my iCloud account I found it had actually updated itself.

But how do I stop it sending me this message?

AND

How are you supposed to contact the server administrator?

Mac OS X v. 10.7.5