Gooner, it's definately a bad url; how are you getting the address? The best way is to right click on the avatar you want then choose properties then highlight and copy the address then paste it into the avatar address in your profile...

where is the site for your picture, and which picture is it?

I think it's not working because access to that picture is forbidden; maybe because you have to use a password to see it, because it's on your own secure site or e-mail or something?