I'm just going to put it out there, please tell me if it's the same for everyone - I have noticed this happening, and other annoying issues that didn't happen before, since I installed Razer Synapse. Anyone else using RS? More importantly, is anyone *not* using it, but experiencing the overlay issue?
Arma 3 for me too.
EDIT: can confirm for me that it's Razer Synapse that's the issue. It was causing my Windows key to open start menu when in-game as well, but when I disabled synapse, it worked as intended and showed no overlay.