Help with a masking transition


I am quite new to flash and am teaching myself how to use it so my terminology may not be so good. Sorry about that.

But anyway, I’m creating a slide transition using 3 simple layers; image1, the mask and image2. The mask is one of those complicated looking ones with little and big circles coming in diagonally (all one layer which does a motion tween from one side of the document to the other). It works perfectly when i play it back but when i preview or publish it it just doesnt do anything, all you see is the first image.

I have no idea what I am doing wrong as when I’ve done this before with a more simpler shape like just an expanding circle it all works.

I’m thinking maybe it has something to do with the mask being made out of lots of items rather than just one, but still it works when i play it just not when i publish it.

Someone help me please!