Is there a secret to distortion free pan and zoom of images?

We’re trying to implement a smooth distortion free pan and zoom similar to the pan and zoom slide show in Windows Vista. I’m using the Tween class for the animation. For zoom I’m tweening the _width property then setting _yscale equal to _xscale in the change event. In parallel, I’m tweening the _x and _y position for the pan motion. I’ve set the quality to highest, the cache bitmap property to true, and the FPS on the Stage to 30. Still, the images show lots of wavy, shimmery distortion on every redraw. The start and destination rectangles for the images is known up front. I tried just tweening the _xscale but that doesn’t translate well when you’re targeting specific rectangles. Maybe there’s some other completey different way to do it I haven’t ran across? Any suggestions greatly appreciated. The way it looks now doesn’t meet the quality bar to actually consider using it for real.

Thanks,
Mark