Scrolling Marquee problem.. (jerky)

I created a simple scrolling marquee for one of my client sites:
http://www.plasticworldincusa.com

Not sure why it is so jerky. I tried frame rate 12 to 32 and its still a problem.

The marquee is just a simple background graphic on one layer and text scrolling on the main timeline about 200 frames on another layer with a motion tween.

Thanks!
Daniel