1010 error when trying to debug, need help

Question

i get this error when i go to debug my site.
TypeError: Error #1010: A term is undefined and has no properties.
     at Index_fla::MainTimeline/frame1()[Index_fla.MainTimeline::frame1:11]
This is the action script
// Startup.
stop();
mainMenu_mc.stop();
// Event Setup.
mainMenu_mc.backward_btn.addEventListener(MouseEvent.CLICK, navigationClicked);
mainMenu_mc.forward_btn.addEventListener(MouseEvent.CLICK, navigationClicked);
mainMenu_mc.logo_btn.addEventListener(MouseEvent.CLICK, navigationClicked);
mainMenu_mc.home_btn.addEventListener(MouseEvent.CLICK, navigationClicked);
mainMenu_mc.goals_btn.addEventListener(MouseEvent.CLICK, navigationClicked);
mainMenu_mc.statements_btn.addEventListener(MouseEvent.CLICK, navigationClicked);
mainMenu_mc.outcomes_btn.addEventListener(MouseEvent.CLICK, navigationClicked);
mainMenu_mc.resume_btn.addEventListener(MouseEvent.CLICK, navigationClicked);
mainMenu_mc.statements_btn.addEventListener(MouseEvent.CLICK, navigationClicked);
// Event Handlers.
function navigationClicked(Event:MouseEvent):void
     //We'll use this to store the Frame Label's name.
     var frmLabel:String = '';
     //Determine what Frame Label to use based on which
     //button was clicked.
     switch (Event.target)
          case mainMenu_mc.backward_btn :
               frmLabel = this.getSequencedFrame(false);
               break;
          case mainMenu_mc.forward_btn :
               frmLabel = this.getSequencedFrame(true);
               break;               
          case mainMenu_mc.logo_btn :
               frmLabel = "home_frm";
               break;
          case mainMenu_mc.home_btn :
               frmLabel = "home_frm";
               break;
        case mainMenu_mc.goals_btn :
            frmLabel = "goals_frm";
            break;
        case mainMenu_mc.statements_btn :
            frmLabel = "statement_frm";
            break;
        case mainMenu_mc.outcomes_btn :
            frmLabel = "outcomes_frm";
            break;
        case mainMenu_mc.resume_btn :
            frmLabel = "resume_frm";
            break;
        case mainMenu_mc.letters_btn :
            frmLabel = "letters_frm";
            break;
     //Find the frame number based on our Frame Label.
     var frmGoto:Number = this.getFrame(frmLabel);
     //Don't do anything if we are already on the requested page.
     if (currentFrame != frmGoto)
          //Get and remember the Home page's frame number.
          var frmHome:Number = this.getFrame("home_frm");
          //If our requested page is the Home page, the flying menu
          //needs to go home.
          if(frmGoto == frmHome)
               mainMenu_mc.goHome();
          //Else, if we are on the Home page and are leaving, then
          //leave home.
          else if(currentFrame == frmHome)
               mainMenu_mc.leaveHome();
          //Go to the requested page.
         gotoAndPlay(frmGoto);
// Helper Functions.
function getFrame(frameName:String):Number
     var frame:Number = 1;
     //Loop through all Frame Labels to find our requested frame.
     for (var i = 0; i < currentLabels.length; i++)
          if (currentLabels[i].name == frameName)
               frame = currentLabels[i].frame;
               break;
     return frame;
function getFrameLabel(frame:Number):String
     var frmLabel:String = '';
     //Loop through all Frame Labels to find the requested Frame Label.
     for (var i = 0; i < currentLabels.length; i++)
          if (currentLabels[i].frame == frame)
               frmLabel = currentLabels[i].name;
               break;
     return frmLabel;
function getSequencedFrame(forward:Boolean):String
     //Used to remember the Frame Label of our page.
     var frmSequence:String = '';
     //If we're looking for the next page in sequence...
     if(forward)
          //If our current page is that last page...
          if(currentFrame == this.getFrame("letters_frm"))
               //...then, we need to go Home.
               frmSequence = "home_frm";
          else          
               //...else, we just need to go to the next frame.
               frmSequence = this.getFrameLabel((currentFrame + 1));
     //...else, we're looking for the previous page in sequence.
     else
          //If we're on the first page (remember, we skipped our Start page)...
          if(currentFrame == this.getFrame("home_frm") ||
             currentFrame == this.getFrame("start_frm"))
               //...then, we need to go to the last page.
               frmSequence = "letters_frm";
          else          
               //...else, we just need to go to the the previous frame.
               frmSequence = this.getFrameLabel((currentFrame - 1));
     return frmSequence;
Can any oen tell me why i am getting this error? using flash cs4 in ac3.

Answer 1

you're trying to reference something that doesn't exist when your code executes.  if line 11, is:
mainMenu_mc.logo_btn.addEventListener(...
then
mainMenu_mc.logo_btn
doesn't exist.