Here is a bug I reported months ago that is still an issue.If you have a slideshow of images that have any kind of transition effect AND a transparent PNG above them to provide a visual mask, the images will pop above the PNG just before the transition, the transition will start and after the transition is complete, the new image will go back below the PNG.Please note, the PNG is not used as a mask layer (like you would do in AS3), it is just a graphic with transparent "windows" to provide a border around the slideshow.