You could be right about the refresh rates. I manually switched my Windows refresh rate to 60Hz, got the same monitor frequency readings as with my earlier post for Linux, (60.2Hz/64.2kHz) and exactly the same distortion, in the same sort of places on the screen.
So what I need to do is get my graphics to sync at 75.3Hz/80.3kHz and all will be fine.
I've looked at the modelines: HOW?
Vendor's website? XIOD does not have one and Samsung does not officially support!