Flickering Grey box?

I had recently downloaded an update for Windows 10 last tuesday, and now it seems that my system is making FF14 misbehave. I've had a direct x 11 fatal error, which is known to these boards, once, but a far more persistent problem is this odd greyish/black box that flickers over perhaps the bottom 1/10th of my screen for an instant? It seems completely random when it shows up, and is somewhat distracting. Am worried that there might be something wrong here with my system, which is greatly distressing since my Nvidia 980 Ti is only a few months old with a freshly updated graphics driver.