Yeah, maybe I didn't explain this very well.
When you first save the film, as long as you manually put the .ahf extension in the name while the 'Save As' box is up, you're OK.
Not doing this results in the saved file having no file extension at all.
And if you happen to forget to put the .ahf extension in the name and save it, then recover from the likely crash, and then try to simply rename the file by right-clicking on it and putting the .ahf in there, you'll crash again when you try to play it.
But I'm still too damn lazy to do this every time