So there's been this long existing problem within flash and externally loaded .swf's where it will continue to play sounds and fire event listeners long after it has been removed from the stage. With Flash Player 10 they've finally brought about a solution with the unloadAndStop() function wich can be called by the Loader class. This in combination with the SoundMixer.stopAll(), should get your external content cleanly out of the way for more content to load.