When you're editing your account to change out your avatar, make sure that after you hit 'save', hit the compatibility button at the top of your browser page (it's a button that looks like a torn piece of paper). After that you should be able to see your new avatar :]

I had this problem too. After saving my new avatar, it didn't seem to work until I pressed ctrl + shift + r (if you're in Google Chrome. Not sure if it works in other browsers.)