setChildIndex making duplicate movieclips?

Thank you ahead of time to anyone who reads this.

I’m working on a flash site with a global navigation that has a drop down. I’m also loading in external swfs occasionally, and when I do, I need to bring the drop down to the top layer.

This is the code I’m using:

setChildIndex(music_mc,numChildren - 1);

Everytime I use that bit of code, it is bringing music_mc to the top, which is great, but it also seems to be duplicating it. I tested this by also having the movieclip move 20 pixels each time I called it, and sure enough, I could see the other instances. I commented out this one line of code, and left in the movement, and the duplications were gone, so I’m pretty sure this is the culprit.

Has anyone seen this before? Is there a way to stop it from duplicating?

Thanks!!!