broken image still showing over correct image

For some reason there is a little broken image icon is showing over an image that is displaying correctly. Here is the code that displays the image.

The image is showing like it should, but it has the broken link in the upper left of the image. I can't figure it out for the life of me.

$url = 'http://'.dirname($_SERVER['SERVER_NAME'].$_SERVER["REQUEST_URI"]).'/img/default_avatar.gif';
		
		return '
		
			<div class="comment">
				<div class="avatar">
					'.$link_open.'
					<img src="http://www.gravatar.com/avatar/'.md5($d['email']).'?size=50&default='.urlencode($url).'" />
					'.$link_close.'
				</div>