Just upgraded from 6.4.4 to 7.4.1 and users who use the threaded mode are really struggling (and complaining, of course) that it doesn't work properly. I've been testing threaded mode on my site as well as here and they are correct, something is amiss. I don't know if I can articulate this problem clearly but here goes:

(1) In threaded mode
(2) In threads which have newfolder icon turned on
(3) click into that thread and (a) sometimes the replies have a corresponding newfolder icon and sometimes they do not (b) if they do have the newfolder icon the system turns off all newfolder icons if you read the bottom or near the bottom reply first. Thus after reading the first new reply there is no way to determine which others are new. This is troublesome if there are many new replies.
(4) Clicking into a thread which does not have a newfolder icon (instead nonewfolder.gif) and often all the replies have a newfolder.gif and the thread operates correctly as you read replies one by one their respective newfolder flag is turned off. If you leave that thread and return later, the system will correctly remember which are read and which are not.
(5) so the problem seems to be inconsistent and incorrect handling of new replies in threads which have recent new replies, in which the system correctly assigns the newfolder.gif icon and the number of new replies at the thread index level but does not correctly assign nor manage the newfolder.gif icon to the corresponding replies that are within that thread.

Probably confusing, but that's a first cut, if anyone is interested in helping to investigate this, I am most grateful and ready to answer any questions that you may have.

thanks,

packlite