Why does the frame around the camera flicker while running the BGE embedded player? Why does the black frame around the camera flicker when playing the game?

Here's a video showing what it looks like: 
https://www.youtube.com/watch?v=7E5S9V1AtHI
I quess this has something to do with the transparency of the area out of the camera region. By trial and error, I figured out that the flicker dissapears when you set the passepartout to 1.0.



However, in my case some of the text objects in the UI still flicker.