[]This is one of those things that I've *never* had happen to me. Usually I can isolate and fix a bug fairly easily but when I can't duplicate it do debug what's causing it, it makes it almost impossible <img src="https://www.ubbcentral.com/boards/images/graemlins/frown.gif" alt="" /> [/]
It goes like this for me:
Locate a forum that has one new thread or post in it, and access it via ubbthreads.php last post.
Then close the browser and reload ubbthreads.php.
The forum will be marked as having new posts, albeit it doesn't, since you took a look at that one post already.
As soon you access the forum via postlit.php, then the forum is marked as having no new posts.