Only reason I saw this was happening was because my Youtube subbox showed the I Love Mondays and 2 Mailbag videos, both of which weren't showing up on the site. Both videos show up under the 'Features' selection but it appears that 'Latest' is now only showing what's under 'Popular'.
I have a similar issue when the "latest" selection is made, the site only returns popular videos.
The issue seems to come and go at random. Sometimes I am able to pull up the latest videos, sometimes it just defaults to popular. I've been able to recreate the issue on Firefox, Chrome, & IE. I've disabled/enabled all add-ons, plug-ins in Firefox without any luck. I have noticed that logging into my account on the site, seems to solve the issue.