Flash CS5: TypeError: Error #2007: Parameter child must be non-null

I just started working with Flash and I am quite lost with this error.

When I bring up the swf file, it seems to be working semi-proper, but I am unsure why this error is coming up.

I am basically trying to make a simple drop down menu.

Here is the script if anyone can look it over and find a problem. Please and Thank you! (this script is on the main page)

var navBtnGlow:GlowFilter = new GlowFilter(0x999999, 0.5, 0, 15, 1, 2, true, false);
navBar_mc.addEventListener(MouseEvent.MOUSE_OVER, navOverF);
navBar_mc.addEventListener(MouseEvent.MOUSE_OUT, navOutF);

function navOverF(event:MouseEvent):void{
event.target.filters = [navBtnGlow];
navBar_mc.setChildIndex(event.target as MovieClip, 1);
dropDown_mc.gotoAndStop(navBar_mc.getChildAt(1).name);
trace(“We are Rolled Over…” + navBar_mc.getChildAt(1).name);
}
function navOutF(event:MouseEvent):void{
event.target.filters = [];
}

----Here is the script for the actual drop down part of the menu----

stop();
theatreframe_btn.addEventListener(MouseEvent.MOUSE_OVER, goBackF);

function goBackF(event:MouseEvent):void{
gotoAndStop(1);
}