It seems there's a bug in the avatar/image system where you cant change back to no image.
How this used to work is you selected to 'change your image' and selected no avatar from any of the lists and changed avatar, making your choice, no image.
Now however while you can change images from one avatar to another, you cant remove the image by the above described,which would normally return to no image.
I've checked with a few others and they seem to be experiencing the same problem.