Hi there, I'm a newbie in here and to be honest don't know if this question has been asked gazillion times before. If so, sorry about that but I've been doing some google action and couldn't find an answer to my question.

I have a curtain in a flash movie that has to be moved to the left, so I did the most simple thing on earth:

I made a symbol with this jpg (the curtain)
frame 1= I added the symbol.
frame 10= same symbol, scaled and moved to the left to pretend that the curtain moves showing what's behind it.
A tweening motion and ..... this optical effect of something that looks like an "interference" appears in every screen that is not a TFT.

I have tried averything, because my client wants this curtain to be moved to one side of the screen so badly, but this interference appears all the time. Does anybody know how can I solve this problem? Or at least could somebdoy please give me an explanation of why this happens and so I will be able to explain it to my client and forget about the moving curtain?

This is a link to the moving curtain, and so you'll know what am I talking about.
Thanks so much!