If it's blurred it usually means its got a tag that's on your filter list.

One of the things I've noticed is that as of several weeks back, if you don't have Javascript enabled in your browser for furaffinity (I use NoScript so I can white-list individual sites for scripting), everything is blurred now. So it looks like blurred is the default image, and there is some check that has to get run in your browser before the real image gets loaded up. (Based on what Llyander is saying above, it may be that tag filtering is being done browser-side, which is actually a smart idea to offload the decision-making from taking up server CPU.)

So honestly if this is happening for random images, it could just be 'there was a network glitch, the real image didn't get loaded immediately, and it isn't until you do something like mouse over the image to get the browser to try again that you see it'.