ActionScript 2.0 :: MovieClips - Implementing Interactive Photomontage Section

I have a minor problem implementing an interactive photomontage section to my site. By that I mean lots of images which can be dragged about by the user to create one larger whole image. Like this (but much simpler, only 12 or so images on the stage): [URL]. So I'm putting the images inside a movieclip as I can use the startDrag and stopDrag actionscript commands so the user can drag the images around.

Here's the code I'm using on each movieclip image:
on (press) {
startDrag(this);
} on (release) {
stopDrag();
}

The problem I have is that I have two photomontages (2 set of images). The user clicks on a thumbnail in the lower right corner to select which one. Each button fades in the appropriate images, and fades out the other set - this is fine. The problem is that obviously the set of images on the highest layer (the Abbey set) are still on the stage but are just faded out (by movieclip tween alpha), so they conflict with the Statue set. Ie. when you try and click and drag an image in the Statue set, you can't get hold of them as you are really dragging the invisible Abbey set around still. I've attached a FLA file which demonstrates this problem. Click on 'BTN1' or 'BTN2' to change the set of images. The Abbey one works fine, but when trying to drag the statue one, the Abbey one if hidden on top will cause problems.

Here's what the section looks like in my project (thumbnails to select which):
Abbey images:
Statue images:

I've tried wrapping the startDrag commands inside an if statement that held a true or false, then put true or false in the appropriate places inside each image movieclip to represent when it is visible or not. I thought this would work, but it doesn't. I also tried putting the set of images at slightly different points in the main timeline, so they were never on top of each other, and then jumping to that point in the timeline when selecting the thumbnails. This kind of worked, but weirdly I had to click twice on the Statue set for them to show (fade in).