I have to admit it has been years since I checked, so this may have been the case for a long while... but the Yahoo Directory pages my site is listed on is graybar for PR.
And the Dmoz site isn't. My sites that are Dmoz listed and not Yahoo listed didn't suffer on Oct 14. My site that is Yahoo Directory listed did. Maybe a coincidence.
But if a backlink profile was heavily dependent on a Yahoo Directory or other historically strong directory listing, then that link was devalued on a given date (say Oct 14), a slip of 4-5 positions across the board would make some sense. Let me get checking some other sites in Yahoo without huge backlink profiles and see if they dipped.
[UPDATE] I just went through an entire category in the Yahoo Directory with a fairly trusted search metric tool and can't find a correlation between any October 14 and a change in rankings for most of the site in that category.