If you need to run Repair on the internal startup drive of the Mac in Drive Genius 4, the drive needs to be unmounted. To unmount the internal boot drive follow the steps below:
Create a BootWell™ drive using Drive Genius 4.
Restart your mac from Startup disk in System Preferences.
In Drive Genius 4 choose your internal boot drive on the left then go to Repair.
If Repair is successful, then you are done.
Quit Drive Genius 4 and do an Option boot. To boot back into your internal hard drive.