Help - Flash 1009 Error

Hi,

I'm using CS5.5. My script is prompting a 1009 error:

TypeError: Error #1009: Cannot access a property or method of a null object reference.

          at _111513Superv4_fla::MainTimeline/kentuckyOut()[_111513Superv4_fla.MainTimeline::frame1:7704]

I see that the error should be in frame 1 of the main timeline on line 7704, but I don't havea line 7704 in that frame. Here is the script for that frame:

stop();

          readmore_state_txt.mouseEnabled=false;

          readmore_state_txt.visible=true;

          state_link.visible=true;

          state_link.addEventListener(MouseEvent.CLICK,linkstateStart);

          function linkstateStart(e:MouseEvent){

                    var nationalReport:URLRequest = new URLRequest("http://www.testsite.org/assets/UnitedStates2014.pdf");

                    navigateToURL(nationalReport,"_blank");

          }

          state_link.addEventListener(MouseEvent.MOUSE_OVER, linkstateStartOver);

          function linkstateStartOver (event:MouseEvent):void{

          var myInputTextFormat = new TextFormat();

                     myInputTextFormat.underline=true;

                      readmore_state_txt.setTextFormat(myInputTextFormat);

          }

          state_link.addEventListener(MouseEvent.MOUSE_OUT, linkstateStartOut);

          function linkstateStartOut (event:MouseEvent):void{

          var myInputTextFormat = new TextFormat();

                     myInputTextFormat.underline=false;

                      readmore_state_txt.setTextFormat(myInputTextFormat);

          }

          testsite_btn.addEventListener(MouseEvent.CLICK, testsiteStartClick);

          singledistrict_btn.addEventListener(MouseEvent.CLICK, singledistrictStartClick);

          function singledistrictStartClick (event:MouseEvent):void{

                    readmore_state_txt.visible=true;

                    state_link.visible=true;

          }

          function testsiteStartClick (event:MouseEvent):void{

                    readmore_state_txt.visible=false;

                    state_link.visible=false;

          }

Help would be appreciated!