Is the avatar you are trying to upload too big. It will give you an error message if it is. Please let me know what error you are getting if you are. Also make sure you are in the right place. There are 2 different places Edit Avatar and Edit Profile Picture. Let me know what its doing I will try and fix it if there is a problem.
I just tried it and it let me upload both an avatar and a profile picture. Please try it again and let me know whats happening on your end. Any errors or anything. I'm sure it being a new board there are some kinks to work out.