When you hit the custom setting with your mouse in the video quality settings after changing resolution in windowed mode and going back to fullscreen
All video settings get reseted.
Hitting the custum button again, Invalid not native resolutions get in there as chosable options and interface resolution gets changed, too.
My correct native resolution (1680*1050) is not anymore choosable.
Hitting default or other quality setting screws it up even more try to use resolutions my monitor does not support, completely unrelated entries.
I could only fix this changing the video memory setting to 1024...Then the correct resolution options appeared again.