Flash / AS3 slide viewer that worked perfectly for years, now crashes live. Why?

After four days of this I'm giving up and asking for help. I have an Actionscript 3 / Flash slide viewer, originally from FlashDen that has worked perfectly for about five years. It STILL works perfectly locally, but I take it live and it freezes and crashes. I know AS3 and I've been through all the classes and got rid of all errors and even the pernickety 'please embed all fonts' output messages. Same problem. It works perfectly locally and it just freezes and goes crap live.  This is obviously a Flash Player 11 issue but I'm totally stumped. There's dozens of images and XML associated with the FLA and the AS3 classes, so I've just added page links, and links to the live swf, in case anyone can find that useful.

This is the original from FlashDen, untouched, just loaded up:

http://www.ksqdesign.com/pgu/PhotoGallery.html

Even the untouched, fresh off the counter version now crashes live, BUT works perfectly locally. Why?

This is my edited version for a client that WORKED PERFECTLY for five years but is now hopeless:

http://www.ksqdesign.com/jansregencystoneiframe.html

http://www.ksqdesign.com/janshfiveiframe.html

The second link uses an HTML5 shell but that makes no difference either.

The thing to note is this app worked perfectly up until a year ago. So it's some kind of FP 11 / security / AS3 clash on the live side that just has me totally stumped.

Very grateful for any light you can shine. Many thanks.

NT