After upgrading to MW 1.24.1 (from 1.21), Special:NewPages now displays zero results. If I create a new page right now, it shows up in Special:NewPages, but anything before the upgrade is not listed.
New pages *are* listed on Special:RecentChanges with an "N" next to them, so clearly something in MediaWiki knows they're new.
I ran maintenance/rebuildrecentchanges.php but it had no effect on Special:NewPages.