I’ve had a lot of problems with Mobile Me syncing my data over the last few months and finally took some time to sit down and fix it. When you spontaneously lose contacts and appointments it can get quite annoying.

If you’re unsure if you have sync problems here are a few telltale signs:

• you’re seeing the same appointments multiple times in the calendar
• multiple contacts
• when you select Groups in the Contacts app, you see multiple sources for the same groups
• when you select Calendars in iCal or the Calendar app, you also see multiple sources

The first thing you need to know which is not at all obvious is that if you are a Mobile Me subscriber, ie you pay your $60/year, you should NOT enable ‘sync calendar’ and ‘sync contacts’ in iTunes. The two processes are redundant. And if you have a Mac desktop, laptop, iPhone and/or iPad, the results can be disastrous, trust me 🙂 In addition, you may sync single devices to multiple computers, I find it’s necessary, this creates even worse results. I have the case where my laptop is the master when it comes to photos, because that’s something you want to always have to hand, but my Mini is the master for music, because you can always sync to a device before you go out on the road.

So after you connect your devices (eg, iPhone and iPad) to the multiple computers you sync to and deselect the ‘sync contacts’ and ‘sync calendars’ options, then hit sync, you will be offered the option to remove the synced data – accept.

At this point your data will not be fixed yet.  In my case the syncing problems caused problematic data sets on my iPhone and iPad.  The trick here is a surprising one.  In the Settings, app, select

> Mail, Contacts, Calendars >Your Mobile Me account

and turn your contacts off.  This will remove the incorrectly synced data on your device, and allow you to set it up again properly.

In my case I was sure that the master copy of my data, ie contacts from Address Book and appointments from iCal, were correct on my laptop, my main machine.  Just to be safe I took a backup before proceeding.

Back on the iPhone, you can now set the contacts switch back to on, and your data will be synced properly.