How to Remove and Reinstall the Apple Mobile Device Service on the Mac
1. Disconnect the iPad or iPhone from the Mac.
2. Click the desktop to activate the Finder, and then choose Go > Applications from the menu bar to display the Applications folder.
3. CTRL-click or right-click the iTunes icon, and then click Move To Trash on the context menu to move iTunes to the Trash.
4. IN the Devices list in the Finder window, click the Mac’s hard disk to display its contents.
5. Double-click the System folder, then the Library folder, and the Extensions folder to navigate to the /System/Library/Extensions/ folder.
6. CTRL-click or right-click the AppleMobileDeviceSupport.kext file, and then click Move To Trash on the context menu to move the file to the Trash.
7. Click the Mac’s hard disk again to display its contents.
8. Double-click the Library folder, and then the Receipts folder, to display the contents of the /Library/Receipts/ folder.
9. If you find a file named AppleMobileDeviceSupport.pkg, CTRL-click it or right-click it, and then choose Move To Trash to put this file in the Trash as well.
10. Hold down OPTION and choose Apple > Restart to restart the Mac.
11. Log back in as usual.
Now open your browser, go to www.apple.com/itunes/download/. Download the iTunes distribution file for Mac OS X, and follow through the prompts to install it.
When the installation is complete, try connecting the iPad or iPhone again.