Wyn called Apple support and they suggested disabling automatic syncing and manually syncing to clear up the problem. That gives a new definition to push.
This seems like a good time to remind people to back up your data before you enable any sort of automatic syncing. Read on after the jump to see how to backup your Address Book and iCal events, just in case.
Thanks to everyone who sent this in and thanks to FailMe for the graphic.
Update: It is 8:30pm on the east coast of the US, and Apple has just posted this note on the MobileMe System Status: "Some MobileMe members may be unable to sync new, edited, or deleted contacts, calendars, and bookmarks over the air between computers and mobile devices (iPhone and iPod Touch). Service will be restored ASAP. We apologize for any inconvenience."
Backing up Address Book
Backing up your Address Book contacts is very easy, indeed. Simply launch Address Book and then go to File > Export > Address Book Archive. This will create a file that includes all the information in your Address Book. Should anything happen to that precious info you can simply import your archive (File > Import > Address Book Archive) and you're all set.
Backing up iCal
Backing up your iCal info is even easier than backing up Address Book. Simply launch iCal and go to File > Back up iCal. Save the back up file and you're all set. If you need to recover from a calendar disaster just hit File > Restore iCal and point it to your backup. Your calendar is saved.