Create a thumbnail data list in XML file and loaded into Flash. This could help you in updating the thumbnail withthout interupt your swf. Check up the below link for using XML in Flash
http://www.kirupa.com/developer/mx20...otogallery.htm
You also can check the sample from my website. Just click on the ADVBOX "Our Portfolio Movie" on the right side in our showcase page http://www.mediasquare.com.sg/ms08r1/ourshowcase.asp. The portfolio image is loaded using XML externally. So I only need to update the data in the XML file and upload the portfolio image to my server without interupt the swf file. This make my upadating job easy.
Hope this is what you are looking for.