Screen flickering in Windows portrait mode

I am attempting to run a game in portrait mode on a Windows Embedded Standard 7 OS. The graphics adapter is the Intel HD 4000 onboard graphics. I inverted the resolution in Player Settings (i.e., 1080x1920 as opposed to 1920x1080), set the app to run full screen and accept all aspect ratios. When I switch to portrait mode (essentially rotating the display 90 degrees) and run the app full-screen on my dev machine with GTX-series video card, I have no issues. However, on the production machine with the Intel HD 4000 graphics, the screen flickers madly, appearing to switch between portrait and landscape modes every other frame. Has anyone run into a similar problem?

I do believe this comes down to your video card driver. No problem with nVidia and ATI, but all Intel HD-series onboard graphics I’ve tested seem to exhibit this behavior.