CMS: WordPress 3.5.1 // Theme: Choices by Kreisi v1.5!prettyPhoto

Bog standard page text content with an image inserted (clickable to display in lightbox).

This works fine in Chrome, FF and IE7 (haven't tested other versions of IE yet).

But in IE8, the image disappears and the <a href> and <img> widths show as 0 when inspected in Developer Tools.

I've searched high and low but can't figure this out. Any suggestions?