So after ALL DAY yesterday trying to figure this out, my problem, the exact same error message, was instantly solved by simply disabling my SECOND VIDEO CARD. Once that was temporarily disabled, STEAM VR and all the apps like Google Earth VR, worked fine.
HOWEVER, I am getting quite a lot of "de-res'ing" and "signal breakup" coming into the headset feed. It seems to be pulsing every one second, with a noticable picture refresh. I am assuming this is the WiGIG data stream maybe getting interference from my wireless router or something.
Hope this helps someone.