Details
Major Description
Just find out using qa.moodle.org: trying to preview a quiz with a password you get error in accessrules.php instead of quiz attempt. There are too many messages to copy there, but you could easily see them previewing http://qa.moodle.net/mod/quiz/view.php?id=35 (I use login teacher password test)
We don't use passworded quizzes, I just reporting catched bug for you convenience.