At one point, I lost the dashboard in the 109e4, but not in other planes. This allowed me to see through the dashboard and see enemy planes, terrain, etc. I could still see the instruments, which were not see-through, but the dash was see-through. It occurred after I had been horsing around with the film viewer, but I'm not sure whether or not that caused it. Changing viewing resolutions to something other than 1024x768 did not alter the behavior. It persisted in Aces High and in the film viewer.
I just uninstalled Aces High and reinstalled it, and that fixed the problem.