I just changed my profile pic on SO using gravatar. It just uses a random generated one, but I have already uploaded my own. The preview shows it correctly, but why is the "main" one not right?
First time, the problem was fixed by hard-refreshing the page. After that, I slightly altered my avatar and uploaded another one there, and disabled the first one.
That time, hard-refreshing didn't help. I had to permanently remove the old one to see the change. That is a bug, in my opinion.