Mediacontroller sound doesn't unload

i am working on a slide presentation, with audio commentary. There are several swf’s each with a separate mp3, which i am playing with media controller. I am loading each swf file on a base swf. Problem is the sound of a particular swf doesn’t stop even when it’s swf is unloaded. So when the next file is loaded, two simultaneous audio tracks can be heard.

i tried putting stopallsounds on the button which loads the next swf, but it doesn’t work either. and i could find only one person with the same problem on a thread, but without any solutions.

any help is welcome,