Keep up the inventive web programming!
I am getting the same error in FireFox, it does not show an image, but instead an image of the URL for the actual image. In IE I am just seeing broken links and viewing the properties results in it showing an unknown protocol and an address of unsaved:///URL. It seems reminiscent of an mod_deflate issue or possibly dynamic image encoding/decoding.
I would also like to note that I am only seeing this issue within the tutorials section.
Have you guys been making changes to the site?