I have the same problem.
Pathfinder -- MacMini DualCore Intel -- MTSVO -- Carnetix PSU 2.2
It was drastically reduced when I started using a thicker VGA cable. I also have a USB VGA Line Driver made by extron installed, which helped. Now it only happens about 10 percent of the time and always after the car has been used a lot that day. (i.e. it is fine in the morning, but if I drive around a lot it starts up at the end of the day).
I will try the iTunes import test, interesting.