the bahavior is similar to http://www.jmonkeyengine.com/forum/index.php?topic=8591.0 “I can go to the main board and the category monkeys are all colored with new postings and I have to go through all of them to find all the post that just disappeared.”
Funny enough, the “Show new replies to your posts” link is woking nicely 
only with me its permanent behavior since about a week or two i guess. its the same on ubuntu 9.04 and windows XP, both with Firefox.
Anyone else having this problem?
greets,
Andy
Have you tried pressing 'mark all messages read' to sort of get a fresh start?
yes it works for the day after i mark the messages read. next workday the problem starts anew. the cookie settings are that the cookies are deleted after they become invalid. in 5 years in this case.
same behaviour here…
the problem seems to be gone at my end. did someone fix it or is it some kind of magic 
i think its magic 