It may be just me and I may be counterintuitive, but when I press the "next thread" I imagine it would send me down the list, not up the list. I usually start at the top of the thread list (newest thread) and work my way down to the bottom (oldest thread on page).

I suppose that I am thinking 'next thread' to mean a thread that I haven't read yet, like it does when I am on the Netscape newsgroups.

I can't think of a textual/semantic fix, so I just remembered what it did.