I tried clicking. Double clicking. I tried the arrows at the bottom. (They even have nice mouse overs that say Next Page/Previous Page.) I tried changing the view type. None of these let me scroll through the presentation.
Based on other comments in this thread I tried putting my mouse on the boundaries of the image. OK, that works. It is a cool idea. But it is an interface that is different from how everything else on the web works. Once you know to do it it is easy. But it isn't exactly the easiest interface to discover when you aren't looking for it. That would be OK if it was just a backup shortcut for people who realized it. But the traditional interface that should be the primary one for people who don't know the site doesn't work. Hence the problem.
The reason that Firefox worked for me is that the browser is in a different place on the screen and therefore I naturally was over the right area of the page. So pure luck.
Incidentally this is the kind of deficiency that is better caught with usability testing than A/B testing. Take 20 people, sit them down with your website, and ask them to complete a task. See what they have trouble with. If you've never done it before you'll likely be shocked at the result.
