Slide Tiles don't work

[Ultrabenosaurus]

I've tried the demo slideshow in Chrome 22, Firefox 13.0, Safari 5.1.7 and Opera 12 on Windows 7 Pro.

With all browsers, when I try the Shift+H shortcut all I see is the bottom-right corner of the first slide, which I can click to go to that slide, but no others. The "By Lea Verou" text is also partially visible in the same place as on the first slide, and clicking it will also go to the first slide.

As seen here: http://i.imgur.com/8esYN.jpg