[Plugin: Magic Fields] Cannot upload image via URL

I’ve added an image field to a magic fields form. The input area says I can select a file or enter a URL. Choosing a local file works. When I type in a URL and click “upload” nothing happens. I thought maybe I had to update the post, but the image isn’t there when I do. This is a great feature and would save me the hassle of downloading an image and uploading it to my site. But it isn’t working.

http://ww.wp.xz.cn/extend/plugins/magic-fields/