[away3d] MovieMaterial error: Error #2015: Invalid BitmapData

[Jensa]

I'm having a strange issue where the MovieMaterial apparently is
unable to extract the bitmap data from a Sprite.

In Flex (AS3 project) I embed my Sprite:

[Embed(source="assets/metro.swf",symbol="metro")]
private var metroMap:Class;

I then instantiate it and put it on stage:

var map:Sprite = new metroMap();
addChild(map);

The Sprite is added to stage and shown as expected. The error is
thrown for the following line:

var mapMaterial2:MovieMaterial = new MovieMaterial(map);

This is the error:

ArgumentError: Error #2015: Invalid BitmapData.
        at flash.display::BitmapData()
        at away3d.materials::MovieMaterial()[/Users/jensa/Documents/Flex
Builder 3/Away3D_src/away3d/materials/MovieMaterial.as:126]
        at Fredrikstadnett()[/Users/jensa/Documents/Flex Builder 3/
Fredrikstadnett/Fredrikstadnett.as:92]

How can a Sprite have "invalid bitmapdata"? Can it be that this sprite
is so big that it can't be converted to bitmapdata? The Sprite is
1730x940 pixels big.

J