The Ed doesn't have any control over avatars. All that happens when you post here is that AB's server sends your registered email address to Gravatar,with a request for the avatar corresponding to that address to be sent back. If the addresses stored on the two servers are different then the system won't work.
You shouldn't be trying to log into an existing account with Gravatar. You should be trying to register a new account (just as if you'd never used the site before).
Just start again, Caran- make sure your email address on AB is updated, set up a Wordpress/Gravatar account using the same email address as you now use on AB and load an avatar. I know it's basically what Buenchico said but I wondered if you'd misread it slightly