I am using AS3 in Flash and I have two scenes (preloader and scene 1). Scene 1 is a button that starts a stop action photography movie when the button is in the "on" state. I have unchecked loop when I exported my swf file, but for some reason, the swf still loops into the preloader when the file is sitting static and not in the "on" state. I can get it to work if I right click on the swf file in my web browser and uncheck loop, but I cant trust that my clients will have this unchecked.
You do need to add the absolute minimum of scripting to your file: In the last frame of your movie, add a keyframe (hit F6). Open the script window (hit F9 fo open/close) and write stop();
Otherwise your movie will indeed loop.
Observe that 'the last frame' in your movie may actually be the first frame. Some movies constructed from pre-built elements will only need one frame to play (and stop).
Hope this helps.
Not everything that can be counted counts, and not everything that counts can be counted.