The AppleUSBAudio.kext is missing an OSBundleCompatibleVersion key in its Info.plist file. This prevents kernel extensions that make use of the AppleUSBAudioPlugin API (as demonstrated in Apple's SampleUSBAudioPlugin sample code) from loading because they cannot then link against AppleUSBAudio.
[h=3]AppleUSBAudio.kext lacks valid OSBundleCompatibleVersion key / 10.7.4 (11E53) and Later.[/h]
Info courtesy of openradar site - this would be a welcome addition to future releases of this application.