Did you upgrade to 2.0.5 Stable or Nightly? I recommend Nightly, which you can find below.
www.joomlapolis.com/downloads/doc_details/640-community-builder-nightly-build
I've no idea what's causing your issue. It seams to be working perfectly fine here. Disable 3rd party Joomla User extensions and see if one could be conflicting. That bind is failing on the dummy Joomla user object when a password is being encoded. Specifically JFactory::getUser( 0 ) is giving you null and it should be an empty user object.
Does this only happen with CBSubs? If you disable CBSubs are registrations fine? For CBSubs to work best on CB 2.x you really need the nightly releases. I suggest installing nightly CB and nightly CBSubs if you haven't already.
If you already have both nightlies and issue persists then please PM backend super administrator login credentials and will take a look.