Scale Tweens in CS4 really jerky

I just downloaded and installed Flash CS4 and I’m thrilled with all the new features. However I am working on a project that uses the Tween class to xscale and yscale a jpeg. this worked smooth as could be in v8 and CS3, but in CS4 it’s jerky and clunky. I’ve made the jpeg smaller but it hasn’t helped.

Have the Tween classes been tweaked or rewritten or something? Anyone else experiencing this?