Problem loading from an attached MovieClip

Question

Project: Flash Professional CS5.5 | AS3
Platform: Mac OSX Lion
Hello:
I have a projector that calls on an attached movieclip with the following function:
function fbtnclicka(e:MouseEvent):void{
var mc:moduleexit_mc=new moduleexit_mc();
The functions successfully loads the movieclip.
I have a button on that movie clip that has the following function:
function unloadexitb(e:MouseEvent):void {
    var loadera = new Loader();
    addChild(loadera);
    loadera.load(new URLRequest("credits.swf"));
    loadera.x = -479;
    loadera.y = -285;
But the function does not load the movieclip. It simply closes the projector.
Any reason why it does not load my movie? By the way it does work if I run the project from the swf but not from the projector.

Answer 1

I used this:
function unloadexitb(e:MouseEvent):void {
var loadera = new Loader();
loadera.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR,errorF);
loadera.contentLoaderInfo.addEventListener(Event.OPEN,openF);
loadera.contentLoaderInfo.addEventListener(Event.COMPLETE,completeF);
addChild(loadera);
loadera.load(new URLRequest("credits/credits.swf"));
loadera.x = -479;
loadera.y = -285;
function errorF(e:MouseEvent):void {
    trace("errorF");
function openF(e:MouseEvent):void {
    trace("openF");
function completeF(e:MouseEvent):void {
    trace("completeF");
and I get this:
TypeError: Error #1034: Type Coercion failed: cannot convert flash.events::Event@2ed92859 to flash.events.MouseEvent.