Apple has released Mac OS X Update For MobileMe 1.1 which is recommended for users running Mac OS X Leopard 10.5.4 and includes general system fixes that enhance your Mac for MobileMe.
Mac OS X Update For MobileMe 1.1 is available via Software Update.
More information about MobileMe here.
[Thanks to MacDailyNews Reader “Jim – TIV” for the heads up.]