Lightbox anomalies

Hi, All.

I have a series of photo galleries on a client's website, which use CMSB and Lightbox 2.0; e.g. www.springflingevent.ca/photosGallery.php?Spring-Fling-2012-Workshops-5. This works as it should on all three major browsers for me - IE, Firefox and Chrome on Windows XP Professional - but when my client views her gallery on her computer and clicks on a thumbnail, the web page disappears and the enlargement replaces it in the same browser window. My client is using IE 9 running on Windows 7.

Any idea what might be causing this, please? I've attached the relevant files.

Thanks!