Mark New Posts as Read

I have been using phpBB for a while now and was looking to try something different.  Something that is a bit more secure.  I was directed to PunBB and I am very pleased.  I've installed it in a test directory and just playing around with it to see what I think and I like.  I like it alot so far.  Of course, I have some reading and learning to do to add more smilies and make some other changes, but I have ran in to one issue and this worries me a little bit.

I created a thread and posted on it by myself about 5 times. But everytime I leave the thread and go back to the index, it still tells me that there are new posts in that thread. I go and read it again and come back to the Index and it's the same.  Still says I have new posts. If I click the button that says Mark All Posts as Read, then it marks it correctly. But once I post somewhere again, it forever tells me that there is new posts even though I have read them before.

Any help as to what may have happened or am I doing something?  Any help would be much appreciated.