I have the same problem, and I have for some time - I would say since Safari 6.0. It *only* happens with Imgur images, so my guess is that Imgur is doing something non-standard when compressing images that Safari's image libs can't deal with. In fact, I often get pieces of images from other open tabs, leading me to believe this is a potential security issue with Apple's implementation. (Though not necessarily, given how it dispatches such tasks to untrusted processes)