AS3 - Shader with Pixel Bender

I'm trying out Pixel Bender but am having an error as follow.

ArgumentError: Error #2004: One of the parameters is invalid.
at flash.display::ShaderData/_setByteCode()
at flash.display::ShaderData()
at flash.display::Shader/set byteCode()
at Distorsion/onLoadComplete()
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at flash.net::URLLoader/onComplete()

The code that I have is

_loader = new URLLoader();
_loader.dataFormat = URLLoaderDataFormat.BINARY;
_loader.addEventListener(Event.COMPLETE, onLoadComplete);
_loader.load(new URLRequest( "distorsion.pbj"));

Then this is the code that throws the error

private function onLoadComplete(event:Event):void {
    // this line c开发者_C百科aused the error
    shader = new Shader(event.target.data);
}

What am I doing wrong?

The pbj file is just some sample file I copied from here http://www.kevingoldsmith.com/labs/PBSynth-v1/sinegenerator2.pbk

Thanks,

Tee