same thing happened with me, heres what i did:
1. make sure that the pic is 50x50 pixels.
2. make sure its under 8kb
if that doesnt work after following the first 2 steps,
3. remove ur current icon (press remove icon)
4. then, add your new icon
if that still doesnt work,
5. go to a different web browser (chrome, firefox, IE) depending on what you have and repeat steps 1-4