Full screen lags with 30 FPS while windowed mode is flawless with 200+ FPS

[CopyrightJail]

Suddenly full screen mode has become unplayable. One day I logged in and all the text is slightly blurry and there is horrible FPS and input lag. I found that putting it in windowed mode fixes it immediately. VSync is absolutely off. My screen resolution is untouched. Ideas on what's wrong?

[SoulhunterIT]

Try to update your graphic card drivers.