Hi Ed,
Please keep in mind that I would be happy to try a beta with a more “verbose” report in the Console.
In the meantime I can report this test:
A) I disconnected from the USB port an RME Fireface UC audio interface, and it disappeared from the list of available audio devices in Preferences > Sound and Audio MIDI Setup. I reconnected it, and it immediately reappeared.
B) I disconnected from the USB port a Logitech Fusion camera (not officially supported by Logitech on the Mac), and it disappeared from the list of available audio devices in Preferences > Sound and Audio MIDI Setup. I reconnected it, and it immediately reappeared.
C) At the same time, the UR824 is not seen among the audio devices (while being connected, turned on and seen by the dspMixFx console). With all other audio devices disconnected, I disconnected the UR and it disappeared from the dspMixFx console. I reconnected it, and it reappeared in the dspMixFx console; but, alas, it was still not among the audio devices.
This test was only conducted on a Mac mini 2011 with Lion (not on my other Mac).
Best regards,
Paolo