Hi Thor,
I'm not AH tech support, so you should probably ignore me, but I did have a problem that acted the same way as you, when I first moved from AH2 to AH3. It was some part of my setting. I removed the AHIII installed, re-installed, but when it asked if I wanted to copy settings, I said NO. Then it ran just fine. I was able to copy my joystick settings and airplanes settings over manually after that, and have them recognized. Maybe worth a try.