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I am currently running iTunes 10.5.1 on a Windows 7 Home PC and when I plug my iPhone 4S into my computer via the USB cable it freezes. iTunes in Task Manager shows up as not responding and after a few minutes it displays the following error:

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

What causes this issue and how can I resolve it?

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up vote 1 down vote accepted

I googled your error message and I found this page and this apple support thread.

Hope this helps !

Edit: Solution #2 in the Lei Mobile site seemed to resolve my issue. I renamed the C:\Users\username\AppData\Roaming\AppleComputer\SyncSerivces to SyncServices_old. I was at least able to plug in my iPhone and perform an initial back up.

I will continue to use to see if that is the permanent fix.

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