Tweened text jumping as it tweens - fix?

Hi - we’ve been given the task of optimizing a CD-ROM piece to be run on the web; I can’t fault the original developer, as his goal was to output for CD play, so giant images should not matter. That said, I totally fault him, as it’s incredibly inefficient to use such enormous images, regardless of the output. I’ve done what I can with my 8 hour budget - the only thing left for me to address is the anomalous jumping going on in certain text tweens (jerky up and down jumping while moving on it’s tween path, versus a smooth motion). A common thread that I see is that wherever a text tween is jumpy, there is an underlying image tween, in the OPPOSITE direction. Can anyone offer either a solution to this quirk, or at least a root cause, to aid me in my diagnostics? Incredibly tight on time - I’m hoping that someone looking at this has encountered this issue before and will know exactly what I’m talking about. Thanks…