Using a Transparant PNG as a mask

Greetings~

I'm trying to use an irregularly shaped PNG as a mask but the mask is just coming out as a straight rectangle, not taking into account the transperancy of the image.

I've found many people complainng about this across the internet, and it is apperantly solvable, I just haven't been able to figure it out.

I've tried Trace Bitmap to vectorize the shape, since it's a single solid shape, but I'm getting weird results: http://www.brightwork.com/~staging2/info/mask.swf

I cant figure out why those lines are appearing across my mask. There's nothing there in the actual traced image, I've even ran the eraser over the affected sections to make sure.

Any suggestions or alternitve ways of accomplishing this would be great!

Using a Transparant PNG as a mask

Why can't you just use a Flash drawn shape?

Using a Transparant PNG as a mask

Basically, I can't mimic that curve on the border as much as I'd like to.

As it stands I probably will end up going for that soloution, but even if I do, it'd be handy to know the answer to the above probel too.

Cheers for the response~