The 10.8.5 update updated a CoreMediaIO plugin that accesses the MBA camera, but didn't bundle the 32-bits version of it. Other (older and newer) versions of the OS do include a universal version (32 and 64 bits), but not 10.8.5. This means 32-bits apps such as Skype or iMovie cannot load the plugin, making the built-in facetime camera invisible to these them.
«Обновление не включает 32-битную версию драйвера для камеры»
Решение: восстановить предыдущий драйвер:
www.imore.com/os-x-1085-breaks-facetime-camera-compatibility-some-third-party-apps-mid-2013-macbook-airs
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discussions.apple.com/message/22979401#22979401 
