[Chip Bergquist]

This fixed it for us:

You must have the preference com.apple.audio.AggregateDevices.plist in the preferences folder. If it does not exist, that is what is causing the problem. In our case, the file was not being created on Premiere start-up because sharing and permissions on the Preferences folder was set to “read only” for the user of that computer. To fix:

Go to HD – Library and single click the preference folder. Select “Get Info”from the file menu. Set the permissions to “read and write” for everyone.

Good luck!