An interesting iOS 5 … uhm, let’s call it a feature, that many users are starting to experience.  Many user will upgrade their iOS device and shortly after, all (or most) of their contacts have magically disappeared.  Did they delete them?  Is iCloud broken? Is iOS no longer syncing?  Aliens? (ok probably not that last one).

Actual answer is all the above (well not the alien one…).First up what users are actually effected.  Most likely people who have this happen are iOS 5 users that still haven’t upgraded their Macintosh to 10.7.2.  These users also have activated iOS 5’s new iCloud, and turned on its contact syncing.  They also most likely, have ignored all the warning signs that say unless you have upgraded everything, don’t enable this.

So what’s actually happening?  When a user enables iCloud’s contact syncing it takes all the contacts in their address book and moves it up to the new universal iCloud setup.  So that’s the good news.  All their files are still there.  You can verify this pretty simply by going to iCloud.com, signing in, and selecting the contact list.

The problem comes in when the user then tries to sync with the computer.  Since 10.7.2 introduced the ability to cope with iCloud, every OS before that starts breaking.  When the iOS devices tries to sync up with what it expects to be iCloud syncing on the computer, it will find nothing there.  As such, it thinks that there are no contacts to sync and therefore removes them from the device.

To fix it you do two things.  The first is to get everything back.  Luckily this is pretty simple.  Go into settings on your device, and select iCloud.  Turn off contact syncing and then turn it back on. it will then pretty quickly download everything again.

Then step two is to decide how you want to sync your contacts.  If you’d like to take advantage of iCloud’s contact syncing turn off contact syncing in iTunes.  If, reversely, you want to continue syncing with your computer’s address book (and don’t plan on upgrading), turn off contact syncing within your iCloud settings.

Granted if you already are running 10.7, just run the upgrade and your problem should be solved too.  Plus you’ll gain the wireless sync features of contacts and calendar with iCloud.  It’s rumored that Apple will be releasing a iCloud patch in the next version of 10.6, so if you can wait for iCloud functionality you can do that too.

Moral of the Story?  It pays to read the warnings and requirement for new features.