AS3 help with buttonClickHandler

Question

Ok, so i am getting the following error:
TypeError: Error #1009: Cannot access a property or method of
a null object reference.
at file_Scene1_fla::MainTimeline/buttonClickHandler()
So here is the code
At frame 75 (intro before hand, works perfectly, with only a
play command)
note: 30fps
var nextSection:String="home";
stop();
firstButtons.firstButton.addEventListener(MouseEvent.CLICK,
buttonClickHandler)
function buttonClickHandler(event:MouseEvent):void {
if ( event.target == firstButtons.firstButton ) {
nextSection="home";
gotoAndStop(nextSection);
} else if ( event.target == home_btn ) {
nextSection="home";
gotoAndStop(nextSection);
} else if ( event.target == collections_btn ) {
nextSection="collections";
gottoAndStop(nextSection);
} else if ( event.target == orders_btn ) {
nextSection="orders";
gottoAndStop(nextSection);
} else if ( event.target == about_btn ) {
nextSection="about";
gottoAndStop(nextSection);
} else if ( event.target == contact_btn ) {
nextSection="contact";
gottoAndStop(nextSection);
} else if ( event.target == americas_btn ) {
nextSection="americas";
gottoAndStop(nextSection);
} else if ( event.target == europe_btn ) {
nextSection="europe";
gottoAndStop(nextSection);
} else if ( event.target == asia_btn ) {
nextSection="asia";
gottoAndStop(nextSection);
} else if ( event.target == oceania_btn ) {
nextSection="oceania";
gottoAndStop(nextSection);
then, i have more objects enter the stage at frame 80
home_btn.addEventListener(MouseEvent.CLICK,
buttonClickHandler);
collections_btn.addEventListener(MouseEvent.CLICK,
buttonClickHandler);
orders_btn.addEventListener(MouseEvent.CLICK,
buttonClickHandler);
about_btn.addEventListener(MouseEvent.CLICK,
buttonClickHandler);
contact_btn.addEventListener(MouseEvent.CLICK,
buttonClickHandler);
stop();
and finally at frame 95
americas_btn.addEventListener(MouseEvent.CLICK,
buttonClickHandler);
europe_btn.addEventListener(MouseEvent.CLICK,
buttonClickHandler);
asia_btn.addEventListener(MouseEvent.CLICK,
buttonClickHandler);
oceania_btn.addEventListener(MouseEvent.CLICK,
buttonClickHandler);
stop();
the error comes, when i try to click on the buttons that
enter in frame 80 (also, the button works as in the up and down
state changes, but it does not move on to the next section of the
website)
from what i got, i have to list the function and all its
possibilities the first time (as in AS3, you can only list a
function once or else get error 1114 (i think thats the # might be
wrong))
then later you list the items entering (as they enter the
stage) or get error 1009, which i still am getting
thank you very much in advance
PS: i only learned Flash this week and have looked through
dark world wide webs for many errors but am finally stumped

Answer 1

ok, the firstButtons.firstButton is a button called
firstButton in a movie clip firstButtons however, the movie plays
(i said a simple play command in the post plays it) and if i click
on it, it takes me to the next section of the website, so i dont
think that's it (note: from what i understand you have to list the
button in that order or else it wont identify it (am i wrong))
the problem starts at frame 80 with the new buttons that dont
forward me on to their given sections
if you can explain what to do next (ie: trouble shoot x or
y...) that would be greatly appreciated as im way way out of my
league
thanks alot