Some button-linking problems

Question

Ok, so this is probably really elementary stuff that I'm about to question. I'm trying to make an interactive video player where you have a choice of 3 buttons and each button links to a different frame that has a video player embedded in it. Once on of the frames are brought up, I have a button to take you back to the main screen. However, after clicking back to the main screen, I'm running into the following output error:
TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at memorialsample_fla::MainTimeline/frame1()[memorialsample_fla.MainTimeline::frame1:4]
    at flash.display::MovieClip/gotoAndPlay()
    at memorialsample_fla::MainTimeline/gotoMain2()[memorialsample_fla.MainTimeline::frame2:11]
Once the above output error occurs, the buttons are no longer active and no longer work.
Here's a look at my code that I have going on:
Frame 1:
stop()
//Link to Frame 2
btn_MJ_Main.addEventListener(MouseEvent.CLICK, gotoMJ)
    function gotoMJ (e:MouseEvent){
        //btn_Beach_Main.removeEventListener(MouseEvent.CLICK, gotoBeach)
        //btn_MJ_Main.removeEventListener(MouseEvent.CLICK, gotoMJ)
        btn_Cloud_Main.removeEventListener(MouseEvent.CLICK, gotoCloud)
        gotoAndPlay(2)
//Link to Frame 3
btn_Beach_Main.addEventListener(MouseEvent.CLICK, gotoBeach)
    function gotoBeach (e:MouseEvent){
        btn_Beach_Main.removeEventListener(MouseEvent.CLICK, gotoBeach)
        //btn_MJ_Main.removeEventListener(MouseEvent.CLICK, gotoMJ)
        //btn_Cloud_Main.removeEventListener(MouseEvent.CLICK, gotoCloud)
        gotoAndPlay(3)
//Link to Frame 4
btn_Cloud_Main.addEventListener(MouseEvent.CLICK, gotoCloud)
    function gotoCloud (e:MouseEvent){
        //btn_Beach_Main.removeEventListener(MouseEvent.CLICK, gotoBeach)
        //btn_MJ_Main.removeEventListener(MouseEvent.CLICK, gotoMJ)
        btn_Cloud_Main.removeEventListener(MouseEvent.CLICK, gotoCloud)
        gotoAndPlay(4)
Frame 2:
stop()
//Linking back to Frame 1
btn_Return.addEventListener(MouseEvent.CLICK, gotoMain2)
    function gotoMain2 (e:MouseEvent){
        btn_Return.removeEventListener(MouseEvent.CLICK, gotoMain2)
            gotoAndPlay(1)
Frame 3:
stop()
//Linking back to Frame 1
btn_Return.addEventListener(MouseEvent.CLICK, gotoMain3)
    function gotoMain3 (e:MouseEvent){
        btn_Return.removeEventListener(MouseEvent.CLICK, gotoMain3)
            gotoAndPlay(1)
Frame 4:
stop()
//Linking back to Frame 1
btn_Return.addEventListener(MouseEvent.CLICK, gotoMain4)
    function gotoMain4 (e:MouseEvent){
        btn_Return.removeEventListener(MouseEvent.CLICK, gotoMain4)
            gotoAndPlay(5)
If you want to see the actual SWF for a better visual at what I'm doing, you can see it here:
http://www.denevi.com/services.html/memorial_tribute.html
Scroll down to the Flash object, it says "Memorial Tribute Samples"
Bonus question while I'm here:
I have the videos streaming, and am not sure how I could get the FLV videos to stop playing when I click the flash's "Return to Samples" button. Right now, the users would have to pause the video if they don't want it to play in the background as they go back to the first frame.
Any help would be appreciated!

Answer 1

Thanks for the response.
Actually, I came to the bottom of this and found that for some reason, Flash CS4's acting a little strange. I have another computer at my disposal with CS3 loaded on it. So I back-saved my project, loaded it in CS3, exported, and all of the buttons worked without any errors. So I'm not quite sure why my CS4 didn't like the code.
And thanks with the FLV stop code, I got that figured out and works. Thanks,
-Billy