How to resolve Adobe Flex error: "Error #2036: Load Never Completed"?
Don't forget you can also add an IOErrorEvent-listener to the loaders, so you can trace a bit more information for yourself. The code beneath is a general starter, it'll probably need a bit more information before it actually works in flash/flex.
swfLoaderInstance:SWFLoader = new SWFLoader();
swfLoaderInstance.source = "someSWFFile.swf";
swfLoaderInstance.addEventListener(IOErrorEvent.IO_ERROR, handleError);
public function handleError(event:IOErrorEvent):void{
trace(event.target);
//etc...
}