I'm in OS X 10.10.5 Yosemite on an older iMac., 27-inch, 2013.
Just really starting to play with Premiere CC . Everything was working for weeks, then this morning I updated firmware for the attached Blackmagic Designs Ultrastudio 4k, which we use to play out from the iMac to the rest of our plant.
Firmware install went fine, but after a restart, Premier ProCC consistently hangs during startup and will not open, beachball city, force-quit.
Premiere CC WILL come up just fine if the BMD Ultrastudio 4k is powered down first. Once the Premiere CC timeline is up, if I power up the Ultrastudio, Premiere CC hangs and must be force-quit. My old Premiere CS 6 install is not affected, but I didn't see if the Ultrastudio could output anything from there. It's really Premiere CC I need to work.
I checked for a CC Premiere update, none available. I uninstalled and re-installed Premiere ProCC, made no difference.
Can you go back to the firmware that worked? Not all updates are good, especially when running older OS versions. When you find the mixture that works, don't change it. Only update if you have problems