[Ryan Webber]

For what it’s worth, I was having a very similar (if not same) issue on my puter and found a solution.

My setup:
2010/12 Mac Pro
3.33GHZ 12 Core
64GB Ram
4GB Nvidia GTX 770 (MacVidCards)
OS X Yosemite 10.10.4
Dual 27″ LED Apple Cinema Displays (ACD) as well as a client preview TV over HDMI.

This issue suddenly showed up for me a few nights ago with the 2015 release of Adobe Premiere Pro CC V9.0. I usually have display #1 setup to show the timeline and typical bins, etc. Display #2 and #3 are set to output a playback preview with Mercury Transit. Suddenly, my second display would only show white when hidden or in another app (could never see the second desktop). Oddly, with ‘Mercury Transit’ enabled in PP I could still work and see the playback preview on the second ACD…well sometimes…it would intermittently go all white. I checked for Nvidia driver updates, none. I removed/reinstalled the app, no success.

My fix was simple and a last ditch hope. Simply enabling ‘Mirror Displays’ in system preferences, then again disabling it, fixed my issue. I hope sharing this helps someone else out. This is the only thread I found on the net that came close to the problem I was having.