I am pondering this querry, and it stumps me. If it works in one, it should work in all missions. Pressing the "U" key will cycle the mission marker/compass, but not the narrator voice. I just flew the entire mission, and she talked to me the whole way. Well, there were long periods of silence over the water at times, but when she was suppose to talk it worked fine for me. I couldn't reproduce the problem you're having. Possibly corrupted sound files??? Reinstall them from the zipfile. That's all I got. Sorry.