The UnreadThreads/UnreadPosts icons don't get updated when you use the browser's BACK button. In other words, if a section or thread has the icon, you go into it, read the post or thread, then use the BACK button of your browser, you still see the original page with the original set of UnreadStuff icons without reflecting the fact that you just read some stuff. Refreshing the page shows the correct info, so it is not a data problem, but a detection+action problem.
And, the reason I am asking for this as opposed to just clicking on the "Index" link at the top of the page: Most mice have the go-back button under your thumb forever. So, I just click that to go back, as opposed to moving the arrow on the screen and then clicking on something.