Odd, but basically the normal boxes have an image surrounding them that gives them the pretty border, and what you are seeing is what it looks like when the image doesn't load. Why it isn't loading for you, I do not know. It's super weird that only these are not loading and not any of the others. I would disable any addons you might have to see if one of them is the culprit. It's definitely something on your end though, sorry to say.