The "use a stock avatar" popup called with
javascript:launch_avatar_window();
on the new user registration page produces a status bar error message and no popup. Not a blocker issue. Once you are already registered and you edit your profile, it works fine.
It looks like the form code for the 'change' link is missing javascript:void(0);" and onclick, or it's just coded differently than the usual popup (like the one on the edit profile page, which works).
The dysfunctional page:
http://www.chessninja.com/boards/ubbthreads.php?ubb=newuser