Adsense in a Lightbox allowed?

Hey,
i want to make a transparent overlay that is put over my Website Content (you can close it easy with a big red hyperlink).
In that transparent div overlay i have a centered div (not transparent), i want to put a adsense ad in this second div.. is this allowed?
i have read in some forums that it is not allowed, but i can't find in the adsense policity that it's not allowed.

i dont frame "others content".. its my content on my website without iframes.
i just have an div over my website content with the div put in it, and you can close that div & see the website content (writen by me).

count that too as "strictly prohibited"?

anyone know the answer?please..