And something of reasonable size (say, a few hundred pixels each side?). Use the change avatar button and Go ahead and use the crop tool to select the whole image. See if it will let you upload, that worked for me.
Nothing was working out for me when I was trying to crop and resize so I finally just started trying different images. I finally found one that worked with no problems. It was a .png image with 150 x 150 resolution.
