Having the same issue w/Cubase Pro 10, Win 10 Pro, i7 8700K, 64GB RAM, 2 x GeForce 1080ti.
Video player window comes up blank white and crashes the entire application, with or without any actual video file in the project. I’ve tried about 5 different graphics drivers, reinstalling Cubase, deactivating SLI, tweaking various Nvidia control panel settings, adjusting various desktop display settings (I’m running two monitors) - nothing works.
My only option is to revert to Cubase 9, which still seems to work fine.
I’ve lost pretty much a whole day of work to this issue, and it’s extremely disheartening.