Is this a different question than the one you asked yesterday?
http://straightrazorpalace.com/site-...-question.html
After you read the last post in a thread, the thread doesn't show up in new posts anymore.
When you reply to a thread you see your new post in the thread; as such it is not a new post anymore.
That behavior was not changed by the upgrade. I wonder if you're used to using "today's posts" instead of "new posts"?
edit: We just
added "Today's Posts" to the bottom of the quick links menu. Try that out and see if you like it better.
