Alex
I had the same problem as "ivylgalum", but I downloaded the text file contribution he put on osCommerce to fix the quotation markand it now works.
However my question is: The readme or installation page says there is a lightbox.css file that has to be installed in catalog/includes/
There is NO such file in the download. I downloaded Advance Popup from your site and then downloaded the contribution from osCommerce as well, but the lightbox.css file in not included in any download.
Is there a lightbox.css file that needs to be included as indicated in the installation file or is that a mistake in the installation instructions

If it's needed, How do I get it?
Somewhat confussed here because the script works without the lightbox.css file incduled..
Greg