EDIT:
Lynne, I have just tried it with the following code added below the "<php" in my config.php:
Code:
define('DISABLE_HOOKS', true);
And it is the same. (the read threads remain there - they just go from bold text to normal text and the image to the left changes - please see screenshot, attached).
I have just tried over on vBulletin.com and it doesn't work correctly over there either. In fact, all read posts stay at the top and remain in bold text.