This has been happening approximately since the front page update.
In Firefox, I only see new posts on the front forum page. Once I follow links down to the individual forums I see nothing later than March 9. "Mark forum as read" is also ignored. "Today's active topics" does work. I tried accessing imminst in Internet Explorer and had no problems, so its browser specific. Clearing cookies/logging out and relogging in did not affect the issue.
- Mey