Missing panel sounds

I am having this problem- when I first load the plane, and am sitting in the cockpit, everything works fine. A good example is the PSS 777, which has an suto shutdown sequence for a cold and dark start, and as the panel shuts itself down, I hear various alarms and whistles going off like they are supposed to. After that, the panel sounds disappear. I haven't been able to establish a cause- I think that either it occurs when I leave the 2d panel or when I alt tab from the game. But anyways, after the initial loading, I am unable to hear panel sounds such as clicking as switches are thrown or the seatbelt sign warning sound or altitude callouts or anything like that. I have noticed this on the Flight 1 ATR, as well as the PSS 777, A340, and A320. These are the only planes that I have installed so far due to a reinstall, so I don't know if the problem affects any others, but will find out soon. And while the panel sounds are gone, I can still hear the stuff int the sound.xxx folder, such as engine sounds and flap noises. ActiveCamera also is succesfully adding in touchdown and roll sounds.I'm running windows 7 ultimate 64 bit. Any ideas?thanks