If you use an Avid MBOX 2 USB Audio Interface, DO NOT UPGRADE TO EL CAPITAN.
The device drivers will no longer load:
10/5/15 9:40:44.399 PM com.apple.kextd[53]: Untrusted kexts are not allowed
10/5/15 9:40:44.399 PM com.apple.kextd[53]: ERROR: invalid signature for com.digidesign.mbox2.driver, will not load
The MBOX 2 worked perfectly in Yosemite.. I'll be downgrading ASAP...
I received the following link from Avid customer support.
Basically MBOX 2 drivers do not work in El Capitan. See below:
http://avid.force.com/pkb/articles/en_US/compatibility/Mac-OS-X-10-11-El-Capitan -support-for-Media-Composer-Pro-Tools-Si…
Only option is to cross your fingers and wait for a fix from either Avid or Apple.. or go back to Yosemite..
Since I'm in the middle of a project and stupidly updated, I'll be installing Yosemite on an external disk in order to get my project completed...
Thank you for your courage