I am glad I found this thread as this problem was driving me crazy.

For my part, I have FF 5.0 on my desktop and FF4.0 on my laptop and both are having the same problem.

So, this morning, I cleared by cache and cookies and it worked, but when I got home, it took me back to a 7:00 AM post even though there were other posts made after it that I read. So, I cleared the cache and cookies again. It then moved me to the last afternoon posts I read. So far, so good.

Logged off to have dinner and returned, launch the browser, clicked a thread and ... BAH.. back to the 7:00 AM post reference above.

Keeping my fingers crossed that you can resolve this soon.

Thanks!