There are two options out there now that may help integrate your Flash 8 file with your Flex project; SWFAdapter and FlashInterface. I would try the SWFAdapter first and see if you can use the simple means of loading and communicating with your swf. I too had some issues with loading a swf through the SWFLoader and the only handler that worked for me was "complete."
Link: http://www.flashextensions.com/blog/2006/12/11/swfadapter-%e2%80%93-proxy-to-communicating-to-flash-8-swfs-from-flash-9/ LD
