Note that there is always a time delay while your gravatar image propagates. It sometimes takes daus to change throughout the internet.
If you are experiencing problems then just to be sure please there are no siiues go to the gravatar site and read the FAQs as it contains common questions and answers to them http://en.gravatar.com/site/faq/
These are the best practices for uploading your gravatar:
(1) Choose an image that scales both up and down in size without losing definition. Prepare the image prior to uploading it and make sure it’s 512 x 512 pixels or larger so it will look the best in the widest range of uses.
(2) The image filetype has to be either PNG, GIF or JPG. Make sure the file name contains only letters and numbers – no special characters – and make sure all letters are in lowercase.
(3) Also make sure the image file name has an extension (Example – image.jpg)
I hope this helps. Best wishes. :)