Last message is not the last message

I read all the issue on this thread and this problem is not related to PHP4, is I am on PHP5, and I tried to clear my cache, but I still can't get this bug to be fixed...
On the forum landing page, the last message of the forum is not the last posted message. I tried to change the publication information and change the dates, I tried to repair the database, nothing, not only it's not the latest message, but it's always the same message that is displayed as the latest one...
Any idea ?