If you're having problems, here are a couple of tips:
1. If Gravatar asks you to assign a classification to your picture, choose 'G'. (The classifications are based upon those used by American film censors. Their 'G' is equivalent to our 'U') ;
2. Check, re-check and check again that the email address you provide to Gravatar is the SAME one which you've provided to the Answerbank. (if you've forgotten which address you used to sign up to AB, click on 'My Profile' and then on 'Edit My Profile' to view it. When you post on AB, this site sends your email address to Gravatar, with a request that Gravatar provides the G-rated picture associated with that email address. If you've used different addresses, the two systems won't be able to talk to each other.
Chris