I ran into this same issue after upgrading to the latest version. After inspecting the page I noticed I was getting Error 403 warnings for the jquery includes. After some digging I found that removing the following lines from the .htaccess file in s2member/includes/ allowed the jquery includes to be loaded and the custom registration fields to be shown again:
<IfModule authz_core_module>
Require all denied
</IfModule>
I mention this more for debugging purposes than a recommendation that you do this as I’m not sure of the unintended consequences of allowing access to this directory.
