Empty MCs and PNGs

I promised I searched before asking this question. :}

I’m putting together the ol’ XML Slideshow but I want to use pngs instead of jpgs. My understanding was that Flash 8 allowed this. When I try and run it with pngs it outputs “undefined”. When I change the xml to load a jpg it works. I’m loading the images into empty movie clips if that helps.

Here is a snippet of actionscript:

bigshirt_mc.loadMovie(bigshirt[p], 1);

And the corresponding XML:

<bigshirt>landscape/assets/shirt1.png</bigshirt>

Like I said, when I change the xml to shirt1.jpg it works. Any suggestions?

Thanks!