I've found some similar posts but not sure if any are addressing quite as complex a structure as I have. If someone wants to tell me I've made this all way too complicated and suggest a better way I would love to hear that as well.

I have a main movie containing a video(flv) and some nav buttons.

On a layer over the flv is a UILoader component.
The nav buttons each load a different external swf into the UILoader (and the buttons also pause the video in the main swf).

INSIDE the external swf that is loaded into the above mentioned UILoader
there is ANOTHER UiLoader component and buttons that load various external swfs into this UILoader.
I did it this way to make the file sizes smaller of each swf.
In this swf there is a button that leads back to the first frame (the "intro).
To this button I added:
Actionscript Code:
backtointro_btn.addEventListener (MouseEvent.CLICK, stopSounds);

function stopSounds (evtObj:MouseEvent) {
flash.media.SoundMixer.stopAll();
}
which works great to stop the sounds that are contained in each of the external swfs.

There is another button that says "back to video", which is contained in the main swf and unloads the UILoader so that the original scene with the video shows again, with the video paused and ready to hit play.
The code for this button is:
Actionscript Code:
closeuil_btn.addEventListener(MouseEvent.CLICK, closeUIL);
function closeUIL(evt:MouseEvent):void
{
    sectionLoader.unload();
    sectionLoader.source = null;
    closeuil_btn.visible = false;
    gotoAndStop(128);
}
I have 2 issues: One is that the UILoader does not appear to be unloading fully because a little while later the sounds in the nested swfs suddenly start playing in the background.
I assume I need to also unload the nested swf's UILoader but am not sure how to reference it.

The other issue/question is:
How do I get the video sound to play again after you return to the video that the Soundmixer.stopAll has stopped?
I know how to do this for specific sounds but not video sound. Do I have to somehow create a channel for the video sound so I can instantiate it and then tell it to play? I'd love a code example...

I realize this is complicated and hope it makes enough sense for someone to be able to advise. Thanks!