Some saved FS9 flights don't re-load at all - Why?

[JSACKS 0]

I've been simming for years now and I am puzzled about one thing with saved flights: once in a rare while when I save a flight and then reload it during a subsequent sim session, the saved situation doesn't get loaded at all, and I am in the same plane and at the same location. For e.g., I was just in the default Cessna at Narita and then I decided to load a saved flight in the PSS 777 at FL400 over France. But when I clicked to load the 777 flight from the Select Flight menu, nothing happened and I was still at Narita in the Cessna.I checked the saved flight file with the 777 and it has all the right details as far as I can see, but it just does not load.Why does this kind of thing happen seemingly randomly (and thankfully, rather rarely!) ?JS