I'm having the same problem, and more:

*** Post tracking works sometimes, and others it doesn't. It doesn't work with hidden forums.
*** Main Index does not update when posting in an hidden forum. Instance.. a post one month ago in my administration forum still shows on the Main Index as the last post, even though a post made today is in there.
*** UBB code does not work when quoting.

Yeah, I have light bulbs on the main index, but nothing lit up in the forum.

Well, actually only some forums (this forum and one other). Others worked as expected.

Does the problem resolve itself if you Mark All Read?

I shall try and see.

Post Tracking doesnt work. I visit this forum today several times. In the overview I see the lightbulb on, I enter the forum, no posting is marked as new but they still contain new replys.

I try the 'mark all read' function but this doesnt solved this.

The tracking function in 6.5.1.1 works better than in 6.5.2

Please review it fast and finaly fix it or go back to 6.4.4. I have 5 month left on my subscription.

Another Bug with Post Tracking:

In the main overview you se a lightbulb on. You enter the forum (this time I see a new posting), use the 'index' to go back (without reading the new posting) and the lightbulb is off now. I reenter the forum and the posting is still marked as new (as it should) but the lightbulb on the index goes not on again.