There are no AJAX-elements around that. Just some outputTexts. MSIE loads the image fine. But even after reloading the page, MSIE only shows the "image not found" icon. And there's no new request for any image to be found (using Wireshark to check). The page itself is reloaded, yes. The image isn't.
Caching is set to always check for new versions of resources. Opera and FF both perform well.
We checked: Upon first load, the URL generated is "only" 1880 characters long. After clicking a link on that image (map), the page is reloaded. And the URL of that image is over 5000 characters long.