I found a huge clue when I saw that page five contains Tom's "God, I'm getting tired of this..." post, which was resurrected by the new activity-grouping feature and brought forward to the front page. That thread exists in two places in the table of contents: Page 5 is its original location in the order in which threads are created, while activity-grouping is determined by date of last activity and makes it show up on the front page as well.

I'm going to have to do some more research into this. The TOC code is gnarly from beginning to end, and I'm not surprised that the design still has some flaws in it.

Thanks for discovering it...seriously, even though I hate finding bugs, better to know about it than to remain dangerously ignorant.