Flash AS3: Null object reference...WHY?

programming flash
1

Hi Here’s my code:

preloaderMC.addEventListener (Event.ENTER_FRAME, startSite);

function startSite(event:Event):void
{
if(preloaderMC.currentLabel == “tapeRollEnd”)
{
nextFrame();
}
}

Why do I get an error of:

“TypeError: Error #1009: Cannot access a property or method of a null object reference.
at MMFinalSite_AS3_2_fla::MainTimeline/startSite()”

I’m just asking it to go to next frame (which is frame 1 of next scene) when it enters the described frame label.

So any idea of how to avoid this error message?