While playing KCDeliverance in exclusive fullscreen mode, if overlay is activated due to an achievement it stays there for ever until I close the game. The same happens if I open the overlay manually using the shift+alt combo. This is worse though as it prevents me from any interaction with the game and I am forced to terminate it from the windows process manager. Also, playing this game in fake fullscreen mode induces terrible stuttering so it isn't an alternative to the ovrlay problem.

My friend is having this same problem.