I was able to find a temporary workaround solution when I stumbled across a post on Facebook.
https://www.facebook.com/Avid/posts/10155064309487525
1. Mount .dmg file - I used the one on the Avid driver page:
http://avid.force.com/pkb/articles/e...k-C400-Drivers
2. Launch the "
M-Audio Fast Track C400 Uninstaller"
3. When the "Uninstallation has succeeded." dialogue box appears, click on "
Quit".
4. Go into
Applications > Utilities > Audio MIDI Setup and your device should be listed.
5. You
may have to unplug and plug your interface back in to get it working again.
I've confirmed when returning the machine from sleep the interface still works.
From this point on,
DO NOT restart your machine. If you do the driver is uninstalled and then you'll have to do the install/ uninstall process in order to get it working again.
Hopes this works for everyone else while we wait for an update.