Responding to an old thread to try and provide insight in to how I fixed a niche flavor of this issue on my machine.
I've been running FAF on a 2-in-1 laptop (with pen + tablet functionality) that was primarily static on my desk. With this laptop, when you physically rotate it it will rotate the screen 90 degrees such that you can take notes, read, etc.
Ended up bringing it along to a hotel, and started having this issue. FAF can't handle portrait orientation, and as a result of my machine being in my backpack vertically for some period of time, it somehow got stuck in a weird state where it was showing that it was landscape on the display settings screen, but some bit was flipped to say that it was portrait. I flipped my laptop on its side once, and then back to normal and everything works fine now.
Hopefully save some other poor soul the headache of troubleshooting that one....