Losing auto pilot

I recently started losing my autopilot after about 6 or 7 minutes of flying. This seems to have happened just after downloading the FS9 update, which did load without any apparent problem. I'll set up a flight, takeoff and set the autopilot which is GoFlight equipment. All of a sudden the auto pilot goes black and can't be recovered. I'm interested in knowing what the possible problem is with my system.I'm using a Nvidia GeForce4 Ti 4600 with 5.2.1.6 drivers.Bill :-roll