CS4/AS3 Video Help!

OK so I have been pulling my hair out for days now trying to figure this out so maybe some of you Flash friends out there can give me a hand.

I am creating a portfolio that has 4 buttons inside the portfolio. These buttons labeled btn1 - btn4 point to specific frames on the time line. At these specific frames I have movie clips which hold flv files in them that I would like to play once the user clicks to that frame.

This all works just fin except for one little problem.

I click on btn1 and it jumps to the frame where I have my first video. The video begins to play. ok

I decide to click on btn2 and it jumps to the second video and starts to play BUT the first video or at least the audio from the first video keeps playing.

If I keep pressing buttons it keeps jumping to the correct spots and the audio keep playing and stacking up on each other in the background.

Does anyone know how to disable a video once Ive clicked away from the movieclip or keyframe that it is house on?

Your help would be greatly appreciated!