Try updating your graphics drivers if you don't have the newest stable one already..
From your images it seems clear that the OpenGL part stays right where it was in respect to the top-left corner of the window (not the just the client-area).. whereas I guess the top left part that was the border before gets the background-color..
Could be a difference in what theme is used in Windows or if there are any window-helper plugins or something that causes the difference in behavior on different computers..
Try dragging another window on top of the window with the error and see if the OpenGL drawn part is properly updated..
I guess you call PumpMessages from a loop and always do glClear and Swap after that?
You could try only calling DefWindowProc always and skip any viewport and resize handling etc as glClear and Swap don't care about the viewport anyway, and maybe add a Sleep(10) or something in the loop to avoid insane update-rates..