iTunes could not sync contacts to the iPhone because the iPhone disconnecte

This worked for me too and took all of 2 seconds. Thanks!

Tim Bobo's solution worked for me. Simplest of them all and it took a few seconds. Happy for now. Hopefully won't reoccur. But if it does, I now know the quick fix.

Worked for me too! Thanks!

I used the "delete iTunes Prefs" solution so that I could still sync the phone data back to the Mac Address Book. Worked on the first try - thanks for the post!

Well, my solution seems temporary. My phone started doing it again today. I set all items to replace the iphone data, and it seemed to work again, but this looks like a bug for Apple. Please report it on the Apple feedback page for the iphone or itunes.

the restore worked for me.

worked perfectly. thanks.

iphone will not sync to any of the mac I have, it will start to sync when I choose address, calendar, etc, and quit in a few seconds, with no sync.
I tried all the recommendations, and as well re-installing clean itunes. Some folks attributed this to the latest Mac OS 10.5.2 upgrade. In any case, anybody could help please, the frustration level is all time high.

Thanks, Gabriel

This solution worked for me also and it brought up a list of conflicts that I had to work through and resolve.

I think the better solution is deleting the itunes preferences. My original solution only works for short time before iTunes starts complaining again. But I thought I would make this clearer. To delete iPhone Backup:

1) On the Mac, open iTunes and choose preferences from the iTunes Menu.
2) Then click on the iPhone icon
3) Use that screen to delete the iphone backup(s) listed.

To delete the reset the iSync preferences
1) Find the iSync application in the applications folder and launch it.
2) Choose preferences from the iSync menu.
3) Then click the button that says "Reset Sync History..."

Then go to iTunes and verify the data syncing is set up how you want it and hit the "Sync: button. Actually, if you make changes, you will see an "Apply" button instead. Click on that.

Now after all of this, you will really want to make sure you do have a backup of your iPhone on the computer. To make sure this happens, you can disconnect your phone, and quit iTunes. Now plug the iPhone back in and open iTunes. The iTunes application will backup your phone again when it does the syncing process.

Hopefully this fix is more permanent than my original post.

I tried the backing up and restoring of the address book but it didn't work, so I disabled automatic syncing of all iPhone in iTunes preferences, and when I connected my iPhone I waited till the little spinning arrows next it in the source list stopped spinning and manually synced... it worked fine.

I don't think it's actually to do with the address book (in my case anyway), because address book syncing was turned OFF, I turned it on before I synced and it worked fine.

This worked for me: Go to Applications > iSync > Preferences > Reset Sync History

Thanks Tim Bobo. iPhone sync solution successful.

Same problem. Have had to Restore my phone 3 times. Solves the problem for a while.

I tried restoring and other fixes, no avail. I used the Tim Bobo fix (see farther down thread) where you delete the backup and reset the history in Isync and it worked fine. Turned out the problem was that I had changed a picture in my personal contact info and this caused a conflict. When I used the one in address book it fixed the problem. Appears that if you have conflicts between existing address cards and iphone contacts it will disconnect.