Error when trying to remove ProgressEvent listener

why does flash return an error (Error #2099: The loading object is not sufficiently loaded to provide this information.) when i try to remove the PROGRESS event listener?

var thumbLoader:Loader;

function createThumbnails():void
thumbLoader = new Loader();
thumbLoader.load(new URLRequest(thumbsXMLList*.attribute("source")));
thumbLoader.contentLoaderInfo.addEventListener(ProgressEvent.PROGRESS, defineBytesCount);

function defineBytesCount(evt:ProgressEvent):void
thumbLoader.contentLoaderInfo.removeEventListener(ProgressEvent.PROGRESS, defineBytesCount); // commenting this out wont return any errors

i am using the ProgressEvent listener just so i can get the bytesTotal… after getting the bytesTotal, i need to remove the ProgressEvent Listener because i only need the defineBytesCount function to run once…