I don't want this to sound like a really serious issue, but this is the best way I could word it. So, what's the scoop?
Google Sites have been acting unreliable since 3/21 when images weren't loading from Google's servers. This affects everything from slideshows to the picture of your cat on your family website. Images are randomly showing up and disappearing with every refresh. It kind of a here and there bug, but it's annoying.
Hope that this is some sort of internal update and will go away soon. =)
Just want to keep all you Google Sites fanboys updated. Here's the Google Sites Help Forum thread: http://productforums.google.com/forum/#!category-topic/sites/E39Hd9YbkDI