Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
iTunes Wifi Sync Introduced to Mac & Windows
In iOS 5 beta 4, wifi syncing is now available on Windows as well as the Mac. Wifi syncing on mac requires OS X 10.6.8 or Lion. You will see an option to enable wireless syncing when you connect your device to iTunes with the USB cable.
- Wireless syncing is triggered automatically when the device is connected to power and on the same network as the paired computer.You can also can manually trigger a sync from iTunes or from Settings -> General -> iTunes Sync
- If you find issues with apps, media and/or photos synced to your device, you can reset then resync. From Settings -> General -> Reset, choose Erase all Content and Settings. Then reconnect to iTunes and sync again.
- In some cases, your device may fail to sync contacts, calendars and account settings, or back up to iTunes. If this happens, reboot your device and re-sync.
- NEW:In some cases, syncing photos may result in only thumbnails on your device. If this happens, unsync Photos then re-sync again.
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