Image thumbnail viewer and layers with chromeless

Hallo!
I’m using a chromeless popup and a thumbnail script.
The problem is that the image from thumbnail is always under the popup.
Here you can see the test site:
[url]http://www.aerreimage.com/1[/url]
Click on the first image on the left in the i-frame, to see the problem.

in specific
I use two livel of chromeless and then the thumbnail.
The first chromeless is on load and full screen.
The second is by click in the center of the full screen chromeless.
Than in the second chromeless there is an i-frame. Inside this i-frame there are the thumbnails images.
When you click this thumbnail (the first on the left is activated), the big image appears behind the second chromeless and not over all.
I try to solve the problem with z-index, but nothing changes.
Probably I wrong to use z-index.

Anyone can help?
Your help is really appreciated.
Thank you

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