Ok, you've a same-origin issue. You're viewing the site without www, but your've live_site specified with www. This causes cross-origin and due to browser security won't allow it to load. Edit configuration.php and set live_site to '' (empty).
Interestingly, when I was trying to update the admin account password after upgrading to GPL 4.0.0 Stable I received a 'namespace does not exist' error (or similar wording) when I click Save and Close. The password did update though.
You need to install latest CB 2.x nightly found below.
www.joomlapolis.com/downloads/doc_details/640-community-builder-nightly-build