Did you try logging in, then back out?
Did you clear your browser cache?
If so, then try this:
Go to your Profile
Click (on the left toolbar) "Look and Layout Preferences"
Make sure "Don't show users' avatars." is not selected. Click "Change Profile" if you change anything.
If its already not selected, then try selecting it, click "Change Profile", and then unselect it, and click "Change Profile" again.
I have had problems with Avatars not fully loading on CH, but, never ones that just dont show up. All is well on my end.