This means the Ajax checker failed. It's just a utility and won't stop saving a user or registrations, but could mean there's a configuration problem somewhere. Please check that $live_site is set to '' (blank) within configuration.php.

Have reviewed the issue and it's working as expected. The behavior is not ideal, but it avoids a previous bug. What CB is doing is immediately causing the ajax checks to fail so the Save action done when clicking the button executes immediately. Previously it would be stuck waiting for the ajax check to finish before saving the profile. I've made a ticket however to address the issue in a more visually appealing way (perhaps hiding the checking all together).