You have this code on the swf first frame
remove and replace it with this code
the way some browsers read flash is slightly different, obviously it is stopping on frame 2 with firefox and therefore not playing any further along the timeline and not showing the animation.
LoadedBytes = Math.round(this.getBytesLoaded());
TotalBytes = Math.round(this.getBytesTotal());
if (LoadedBytes == TotalBytes)
you might also want to put the classid back inside the object tag classid="clsid27CDB6E-AE6D-11cf-96B8-444553540000"