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Mac Fix: iTunes was unable to load dataclass information from Sync Services.

Last week was a fairly big one for the iPhone stack, what with the release of iTunes 10.2.1 and subsequent release of iOS 4.3. Of course, I dutifully installed both. A fairly painless, if long-winded exercise.

I noticed a couple of days later a problem syncing my phone with my MacBook Pro. On connection of the phone, iTunes displayed the following error message:

iTunes was unable to load dataclass information from Sync Services. Reconnect or try again later.

Well, I did and the same message was displayed next time. So, I rebooted the MacBook Pro and, for good measure, rebooted the iPhone too. On connecting the phone (once iTunes had started up) - no change. Same message.

On closer inspection, it looked as though the phone was actually syncing but not backing up. Not a situation that I was happy with, so time to start investigating seriously. After much trawling of the usual haunts (starting with my search engine of choice, naturally), I uncovered both the cause and the fix, though the relationship between them isn't especially obvious. While I supposed that the issue lay with either iTunes 10.2.1 or iOS 4.3, there was another little detail that I hadn't noticed (and have thus far neglected to mention). Shortly after these upgrades, Apple posted the latest version of XCode to the Mac App Store. Despite not yet having built a real iOS application in anger, I couldn't not have it, so I clicked the button, entered my Apple password and let XCode install. It was XCode, it appears, that was the root of my synchronisation issues. The connection may seem tenuous, but I suspect it could well be related to the inclusion of the iPhone emulator replacing important files.

The solution was found on Apple's support site, here: iTunes: How to remove and reinstall the Apple Mobile Device Service on Mac OS X

Basically, it involves uninstalling iTunes, removing two Apple Mobile Device Service files and reinstalling iTunes. You'll be especially pleased to know, if you have to go through this process yourself, that all of your iTunes content and configuration remains unharmed.

 


Posted Mar 14 2011, 02:57 PM by Steve Morgan
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Comments

Max wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Wed, Mar 16 2011 1:07

Thank you!  I just upgraded to the new Xcode too, and that must have done it.  The steps above worked perfectly, unfortunately I didn't find them until after I restored (which sucked because I didn't have a sim in it, it's just a development device).  

Bill M wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Tue, Mar 22 2011 11:38

Thank you! Same here, my Xcode upgrade would not have come to mind to create this issue. Thanks for the post, frustration solved!

Vicki C wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Tue, Mar 29 2011 13:57

Thank you! I must admit it had crossed my mind to wonder if it was installing XCode 4 that had caused the problem as I was fairly sure I'd synced since upgrading to 4.3. Cheers for the advice.

Mustafa wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Tue, May 3 2011 8:08

Thank you.

useEvil wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Thu, May 12 2011 21:55

Thank you as well! I knew it had to do with the new xCode, but didn't know how to fix it. I found I only had to trash the kext and run the iTunes installer. I didn't have to restart or uninstall iTunes.

Jay B. wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Sun, May 15 2011 13:44

I couldn't find anything usefull on the internet until your post, THANK YOU SO MUCH :-)

Robert Snapp wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Sat, May 21 2011 6:29

Thank you Steve!!! The same problem happened to me after installing XCode 4 yesterday. I was lucky to find your solution before I was started pulling out my hair. One would think that Apple would have patched this problem up between mid-March and mid-May, but apparently not.

pt2ph8 wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Wed, May 25 2011 22:34

You rock! Wasted an hour until I found this post. It worked! Thanks.

Remarksman wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Fri, May 27 2011 0:13

Thanks, I suspected xCode 4 right away because this cropped up immediately after installing it. So far xCode 4 sucks compared to xCode 3!

Justin wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Sat, May 28 2011 14:32

Thank you so much!

fu wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Wed, Jun 22 2011 17:02

So you post only glowing praise? What about fairly earned criticism? Your article, although helpful, left out several key items of information.

1. You seem to suggest that it was the omission of installing Xcode that led to the error. Yet, all the commentators seemed to suggest that the new Xcode WAS the error. Which is it?

2. You failed to properly identify whether you authorized and installed the new Xcode to your iphone or your mac. Which is it? That is a very important detail.

3. How does the "fix" of installing Xcode relate to your later instruction to uninstall itunes, delete two amd service files, and then reinstall itunes? What is the connection? Or, did you initiate two otherwise random "fixes" and you're not sure which resolved the issue?

4. What about this issue on a PC? How about the fact that this is a very prolific error across multiple versions of itunes and possibly all generations of iphone?

5. How is it that I had not synced my iphone for months and months (after my last smooth, successful sync) and this error "suddenly" appeared when I decided to update contacts and music the other day? In fact, I tried to re-sync on two different computers with two different versions of itunes? The only variable that changed was that I upgraded my 1st gen iphone from OS 3.0.2 to 3.1.15.

I really wonder sometiems if Apple initiates some kind of automatic communication with all versions of itunes out there and "checks" if they were the "latest and greatest, super duper 10 point whatever" versions and installs a sneaky little "fix" if they aren't. How else do you explain itunes and syncing working like magic for so long, and then suddenly problems pop up?

Anyway, please consider above issues and repost. Thanks.

Nick wrote re: Mac Fix: iTunes was unable to load dataclass information from Sync Services.
on Thu, Jul 7 2011 19:11

Thank you - yr fix sorted out the problem. I too downloaded Xcode 4 and then had the sync issue the day after. I have OSX 10.6.8 so only needed to delete iTunes and the kext file, then download iTunes 10.3.1.

Fu, yr criticism is ill-informed and rude. Please repost...

Steve Morgan 2008. All rights reserved.
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