I have recently started accessing models via the Access Point using Safari on a MacBook Pro (Mountain Lion 10.8.3). Everything works perfectly. I used to access the QMC using Google Chrome and that worked, but when I click on anything in the QMC in Safari I get an error message - "Invalid Request: Root element is missing."
Okay, it seems that Safari 8.0 it is not supported yet, We currently support 7.0 of Safari, for that you might encounter all kind of issues with Safari 8.0. As workaround try different browser like Chrome or FF.