How can I fix syncing problems between MobileMe and the iPhone?
UPDATE: MobileMe has been superseded by iCloud.
Sometimes MobileMe will have problems syncing your data across multiple devices. Ideally, the service will keep ten items (Bookmarks, Calendars, Contacts, Dashboard Widgets, Dock Items, Keychains, Mail Accounts, Mail Rules, Signatures/Smart Mailboxes, Notes/Preferences) synced between your computers, iPhone and other devices. When and if this process stops working properly you can try the following steps to reset your sync.
1. First of all, always back up your data. You can also back up your Contacts in the Address Book on your computer by choosing File -> Export -> Address Book Archive. Save your Calendars in the iCal application by choosing File -> Back up iCal.
2. Check Apple's MobileMe support page to make sure the service is up and running.
3. Log into your account at Me.com and make sure your Calendar and Contacts data is correct. If your data is on the cloud, the problem is with your computer or iPhone.
4. Double-check that you are seeing all of your Calendars. On the iPhone, open the Calendar app then touch the Calendars button in the upper left hand corner. All calendar types should be checked, meaning they are not hidden.
5. You can reset your sync history in iSync on your Mac. Go to Applications and run iSync. Choose iSync -> Preferences from the top menu. Click the Reset Sync History button. Quit iSync and try a MobileMe data sync to see if the problem is solved.
6. The next step is to open System Preferences -> MobileMe -> Sync -> Advanced -> Reset Sync Data. This dialog box lets you copy the specific type of data you're having a problem with (Calendars, Contacts, etc.) to the location where you're seeing the problem. For example, you can replace all Contacts data on your computer with Contacts data from the MobileMe server. If you know where the latest version of your good data is stored use this tool to copy over the bad version.
7. If the problem persists you can try to reset sync data on your iPhone (or other iOS device). Navigate to Settings -> Mail, Contacts, Calendars -> MobileMe. If a good copy of your data is stored on a computer or the MobileMe server, you can turn OFF Bookmarks, Calendars, Contacts, and/or Mail. When prompted, tap the Delete from My iPhone button to clear the data you're having a problem with from the iPhone. When this is complete, turn the data type back ON and the iPhone will download freshly synced data from the MobileMe server.
8. If none of the above options works, you may have to visit Apple Support Article TS2481. This lengthy document details advanced procedures for troubleshooting Calendar and Contact syncing.