Garageband 10 Audio Unit gone I am trying to use an AudioUnit plugin that requires a USB security authentication key. The first time I installed the Audio Unit I didn't have the key. When I received my key and authorized the software (Antares Auto Tune with the iLok USB key) the plugin did not show up. 

I attempted to remove the cache files to force Garageband 10 to find the plugin but none of it worked. 

The strange thing though is I can open Garageband 6 and the plugin shows up and if I create a new account on my computer the plugin shows up but this is suboptimal.
I received a response from Antares with the answer


  Once you are in the "Library" folder go to: 
  
  Caches/AudioUnitCache/
  
  Delete the “com.apple.audiounits.sandboxed.cache" file.
  
  Go back to the Library folder, then open the Preferences folder
  
  Once you are in the Library/Preferences folder, delete the file
  "com.apple.audio.InfoHelper.plist"
  
  Empty your trash and restart your computer.
  
  You should now find Auto-Tune 8.1 in GarageBand.


This solved it for me.