Casting a 3d movie clip

Hello All,
I’m new to flash and actionscripting (i come from the land of ansi c but have traveled extensively). I’ve created a great animated animated 3d movie clip and want to have them generated on the stage in relation to an xml file. I’ve gotten this to work with a 2d movie clip but am running into problems casting a 3d object.

my object (a movie clip - boxContainer with an instance name of boxContainer_mc) is built out of all movie clips in the following way (shown in tree form):

boxContainer

-bottomBox
—boxFront
—boxLeft
—boxRight
—boxTop
—shadowFront
—shadowLeft
—shadowRight
—gradientLeft
—gradientRight
—gradientFront

-topBox (this movie clip contains an animation that is controlled through a MouseEvent:Click inside of its own actionscript)
—left
—right
—top
—back

This animates smoothly through flash, but doesn’t work when I try to cast the movie clip in actionscript 3 using the following code:

var boxContainer_mc:boxContainer = new boxContainer();
addChild(boxContainer_mc);

When I try to test the swf file I recieve the following errors:

1046: Type was not found or was not a compile-time constant:boxContainer
1180: Call to a possibly undefined method boxContainer

any ideas?