Problems with Blur on Tweened MC

Hi all, was hoping someone could point out what Iam doing wrong. I have a slot machine style tumbler that rotates (picks up speed and finally stops). I placed a very exagerated blur keyframe in the middle and it looks great inside the Flash CS3 authoring environment - but if I test or publish it the effect is gone???
Someone lese in the forum said they had problems because the underlying mc was made up of png images - which I also have - could this be the issue?
I am publishing for flash 8+

Any help greatly appreciated :slight_smile: