glutPassiveMotionFunc & Glut Game Mode

Hi all!!
I have another problem…

I use glutPassiveMotionFunc to control the camera with the mouse, like in a First Person Shooter.
I found an example of doing that on internet.

In a “Glut Window mode” works fine, and doing a FullScreen too; but when I use a “glut game mode” this function (glutPassiveMotionFunc) makes the game do strange things: I can see the game at the beginning, only when I move the mouse a lot and wait few seconds… the game is showed, and sometime the game exit.

Someone know the problem with glutPassiveMotionFunc and glut game mode???

or any solution??

thanks all.