I'm using post type orders 1.5.7 with WordPress 3.5 and the included theme Twenty Twelve.
In the theme admin under Appearance > Headers - theirs a feature where you can upload header images, then select "Random: Show a different image on each page" from the options. When this is selected and the plugin is active, no image shows in the front end. De-activate the plugin and the random images show.
As a note this only happens when the plugin is set to Auto Sort.
This is a fresh install, with no posts and no other plugins.
Any help would be greatly appreciated...