Vertical black bars on 2560x1440?

[ImRocket Man]

Does anyone play with the resolution 2560x1440? I have vertical black bars on the sides of the screen.

 

But, I'm pretty sure I didn't have this before. I pressed "Win" key by mistake, so it showed the desktop, and since then, the game has these vertical bars.

I tried to change resolution, then set back to 2560x1440, re-enable and disable Vsync, disable full screen, etc...but nothing changed.

Now, it also seems to stutter a little bit when I move mouse cursor to the edges of the screen.