When looking at the results of a quiz, it was possible (Moodle 1.6.2) to view only students that had not made any attempt of a quiz using the drop down menu at the bottom of the Quiz results page. However, with Moodle 1.8, although the pull down menu exists, selecting "Show Students with no attempts only" does not display any students even though there are students that have not done the quiz. The message "Nothing to display" appears.

I know this because a few months ago I moved my Moodle installation to a new server. The old server is still running with all the old courses so I am able to compare identical courses on two different Moodles: 1.6.2 and 1.8+. Also, the gradebook in the new system shows me that some students have not attempted the quiz, yet this fact is not reflected in the Quiz results.