Passing over the various idiosyncracies of the interface, which I accommodated myself to, I think I've come up against it with an 18 Meg upload. It always times out with a 504 page, but the image is there. However, the smaller images, including the thumbnail, are not created. ( These don't seem to be mentioned anywhere, and it took me a while to realize that they were there, but now I rely on them. ) Since the thumbnail is not produced and stored, it takes several minutes for wordpress to produce it on the Media page. I don't know why this is happening, but I assume it's some kind of timing issue. This large image is useless without being able to use a smaller image to represent it in a post, so what recourse do I have?