Have been running ACC for a year using Oculus Rift - all good. Just replaced the Rift with a new HP Reverb G2 headset, ran thru the Mixed Reality Portal setup and it works fine, tracks cleanly etc. in the portal. Start up ACC - disaster. I select "run in Steam VR" mode and it takes me into a kind of hellscape in the roof of the garage menu. I can see the 2D menu far, far below me but cannot recenter the view with the default or my programmed commands. The image lurches around, flickering on and off and without any smooth tracking of the headset. So I can't get past the garage menu and it's clear something is horribly wrong with the headset operation in the game. I have looked thru in-game settings in 2D mode which won't let me access any VR settings, and my Steam VR settings, without seeing any clues about what is wrong. Any suggestions? Thanks.