1. jeffrey7's Avatar
    I cant restore and upgrade my iphone 4. It occurs error 21. Any guides?
    2011-12-29 09:36 AM
  2. hcgaloi's Avatar
    Error 21 means that you have an older version of iTunes when upgrading to iOS 5. It need to be at least on version 10.5.1. I suggest that you install the latest

    Good luck
    2011-12-31 07:23 PM
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