There seems to be some Gremlin. I just read everything in my "Unread Topics" posts, & when I went back to to the "Index" there were several that I hadn't read there (even after a refresh). I'm also on firefox.
In looking at it closely. I didn't finish everything "unread" last night, but the items that I didn't read then, do not appear when I go to the "unread topics" today even though they remain "unread" on the Index page.