hw123,
Sounds to me like you have an overheating problem on your graphic card.

I just installed AFPD a few days ago and I am over the moon with it but I have noticed that my cooling fan works very hard for this simulator compared to many other game or simulator apps.

Last summer I had this prolem on one of my computers. As a quick test, I took off the PC cover and placed a desk fan near it blowing over the motherboard. Worked a treat so I knew immediately where my problem lay.