Unexplained Error #1009 when calling a function in a component.

Question

I created a component that allows you to display a song
listing.
I need to create various instances using it's constructor,
then add them to a main scrollbar control.
Before putting it in a loop, I wanted to make sure I could
add a single instance, with this code:
var NewListing:mediaUnit = new mediaUnit();
NewListing.setArtist("In Flames");
NewListing.setAlbum("Come Clarity");
NewListing.addSong(1,"Take This Life");
mediaLib.addObject(NewListing);
Compiled, ran, got this:
TypeError: Error #1009: Cannot access a property or method of
a null object reference.
at mediaUnit/addSong()
at MC3_PORT_fla::MainTimeline/MC3_PORT_fla::frame36()
Okay, maybe it's the code of addSong, right? So I commented
it out so it's basically:
public function addSong(id:int,song:*):int {
return 0;
Still gives the error.
Why do setArtist and setAlbum, being in the SAME exact scope,
not give this error? It just doesn't make sense to me.

Answer 1

Alright, I got it pinpointed. addSong calls
var movie:MovieClip = new units.mediaUnit.songItem();
Which Flash seems to consiter null.
Not like anyones going to bother reading this, everyone on
this forum tends to be lazy as hell, but anyone willing to help,
I'd appreciate it.