Just wandered into the same problem: flash embedded in a popup layer, works in Chrome, Opera and Firefox, but not in IE8. The layer won't even appear. Nothing happens. Tried it in IE6 and 7, no problem. Tried downsaving the animation in SWF7 & 6, thinking maybe it was the newer filters in SWF8, but no luck. No wonder people are dropping IE8 in droves.