IDE :: Flash Loading Differently In Browsers

I have one swf, and roughly 4 or 5 classes. when the swf loads, the document class places 3 movieclips onto the stage- one of them animates across the screen. Using the tween class, I listen for the COMPLETE tweenEvent, which when triggered, instatiates a slideshow class. the slideshow class loads in a series of pics.On safari(mac), linux, no issues. on firefox(mac), the 3 mc's never appear, but instead, there is the same time delay as if the animation did play, and then the pics DO load. my client says everything works fine on first load, but returning back to the page after navigating away causes the same problem I described above. THey are on IE- probably 7.