Updating 'No New Posts' Icon

[crashys]

Hi, I'v previously used the phpBB forums, and when I got to vBulletin I found something weird, after I read a certain topic I press the 'Home' button and when I get to the index, I still see the 'New Posts' icon and its the exact same post that I read...the only way to clear this is by pressind 'Mark Forums as Read', or by coming all the way to the beggining manually.
My question is, if I can get the icon to update has soon I read all the posts on that determinated sub-forum, I'v ran all the options and can't find nothing to fix it and its pretty annoying :s.

Thanks to all in advance for your time and help.