I don't see the flash on opening in either IExplorer or Firefox. I don't know if the following applies to your site, but I see in the view source your flash object won't start by itself.
I know awhile ago, due to some legal bs microsoft broke the way flash starts - which broke many flash sites, & flash intros similar to yours. What broke was now you have to click on the flash object to start it. Most people don't understand & everything got out of sync.
I had this same problem on my Walter Mitty site with the Flash Books. A visitor could not start changing the pages without first clicking anywhere on the book, then on the corner to drag the page open. Intuitively, you would just turn the page; the extra click killed the workings.
I found many solutions, but this one works for me:
http://www.bobbyvandersluis.com/ufo/My books no longer require that first click on the object.
I don't know if this applies to Firefox or not. Perhaps after Microsoft fell, so did Firefox.
I hope this help, or even makes sense.
Edit: Credit is due; it was philvis who pointed this out to me in the page turn thread below.