The window opens, says "Unbound - Early Access v0.2.4 (Not Responding)" in the title bar

blank white screen.  With a popup window that says "PlayEngine.exe has stopped working"

app does not start

Windows 10/1080 GTX

C:\Program Files (x86)\Steam\logs\vrclient_PlayEngine.txt ends with

Tue Jan 09 2018 08:07:27.444 - //===================================================================================================================== Tue Jan 09 2018 08:07:27.445 - vrclient startup with PID=1176, type=VRApplication_Scene, config=C:\Program Files (x86)\Steam\config Tue Jan 09 2018 08:07:27.447 - [Settings] Load Default Json Settings from C:\Program Files (x86)\Steam\steamapps\common\SteamVR\resources\settings\default.vrsettings Tue Jan 09 2018 08:07:27.447 - [Settings] Load Default Json Settings from C:\Program Files (x86)\Steam\steamapps\common\SteamVR\drivers\htc\resources\settings\default.vrsettings Tue Jan 09 2018 08:07:27.447 - [Settings] Load Default