MoZo1 -3 Junior Poster

Well, so I import a transparent gif into flash, put it into the stage, make animation, etc., then hit publish, select gif, on the gif tab set up looping, and I set transparent to transparent (not opaque), and thats it, I publish. But then there is no error message, and no transparency. Whatever I set the background color of the stage, it stays on the image behind the gif (so I know that the gif was really transparent, cause I see the background). However when I publish the same thing to png, then there is transparency.
I've tryed different settings with opaque, transparent, and whatever, searched the web, and I couldn't find out.
I'm using Flash CS3. Thanks for the help!