I thought it might be of help. I'm testing the script in a SSL protected site and I was getting a security warning while requesting the gravatar image. I've been searching this forum and the knowledge base but I didn't find a solution for this.
Anyway, after a little bit of research I found the PHP files that do the requesting:
Yeah, by default every external resource (like gravatar avatar) is pulled from http... currently this needs to be changed manually but in the future we might add auto detection of the (secure) protocol.