Well, I wrote to him and this is what I got back:
It sounds like a problem with anti-aliasing. It could either be from the version of the driver you have installed or for something in your settings that needs to be fixed. Go to the stereo properties in to the 'stereo compatibility section' and check the box that says "turn off anti aliasing for stereo"
Also, underneath the stereo properties menu item, go to "Performance and Quality Settings" and turn Antialiasing to OFF.
Best Regards,
Nathan
eDimensional, Inc.
It's working for me. The only problem that's left now is, that FS doesn't react properly to my controler whilst in 3d mode. I have discovered two planes so far with the joystick problem - the douglas and the cessna. The others are working fine. I can't imagine, why those two don't react to the joystick if I change nothing else than the graphics.