I am checking the Forum and the "What's new" display at the top tells me I've got 2 messages. But when I click there, I am told that I have no unread messages. I don't remember this happening before.
Yes, it has happened to me several times. It seems as though if you just click on the header and don't read the posts it doesn't clear the what's new register immediately.
I get a bunch. I've read through all the new posts yet still have several that says unread. After going through them all I usually have to click "Mark Forums Read" to get rid of it.