Hi dran_sy, this should solve the problem:
Make sure GarageBand is closed. Go to your ~/Library/Caches folder (this can be found by clicking "Go" in the Finder menu bar while holding down the option key), and delete the com.apple.audiounits.cache file located there. Then, open iLok Manager and make sure the UltraChannel License is activated on either your iLok dongle or computer. Launch GarageBand, and you should be good to go! GarageBand will need to rescan your AudioUnits folder, but this should solve the problem.
Let me know if that doesn't solve the problem.
Tom Longabaugh
Eventide
