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If you have not updated to Apple Configurator 1.3

If you use OS X Lion, continue to use Apple Configurator 1.2.1, or upgrade to OS X Mountain Lion.
 

If you have updated to Apple Configurator 1.3

If you still have a copy of version 1.2.1, you can revert to it and restore the previous database files with these articles:

• Apple Configurator: Backing up and restoring data
• Apple Configurator 1.3: Updating from an earlier version