Smooth Tweens ?!?!

Hi Everyone!!!
I hope you’re having a great day, first of all…!

I am designing a movie with a simple jpg moving from left (outside the stage)
to the middle of the stage. Then it stops and when a button is clicked
it simply moves to the bottom (outside the stage) to “dissappear”

I see it perfectly fine on the web with IE 6.0, but on Netscape … it sucks!

[color=#003366] (in case you wanna look)[/color]

I have someone who told me that on their end (miles away from me)
it looks “choppy” and “jerky” and just not smooth no matter what
browser (ANY!) or platform (MAC, WIN) combination.

Does anyone know a way to avoid this ???
I’ve never come across this before…