I tried changing my avatar using a url to my webserver and I get this error:
The uploaded file is not a valid GIF, JPG, or PNG file. Please ensure that it is and try again.
The file is in fact a JPEG and is using the correct extension. A couple other times I tried it couldn't find the url. I know the path is correct by using in a browser which displays the picture. The image is also cropped according the limitations. I'm not a newbie to all this!! Is this a known issue? I'll try again later after the image has been up for a while.