Apple USB ethernet adapter is not detected
I had the same problem and a couple of minutes ago I saw something about the "Android File Transfer Agent" having problems with the device. So uninstalled "iSyncr" software (sync android over Wifi), disconnected the usb device, plugged it again and now it's working fine.
https://discussions.apple.com/thread/3941878?start=0&tstart=0
I've resolved by simply create a new location in Network Preferences and then try connecting it again by clicking "Apply" on this new location.