Following up on the fact that the page seems to work in IE8, I tried adding:
<meta http-equiv="x-ua-compatible" content="IE=8">
to header.php immediately after the <head> tag. This fixes the problem!, but other pages don't render as well. Is there a way to inject this <meta...> tag just on tiled gallery pages?
I've removed the <meta...> tag so you can still see the problem.