As far as I know, that feature has never been enabled here at the TMF. I 'could' be mistaken, but it has never been a working function since I became a member, which was back in Oct of last year.
I could be wrong but i believe i read at one time it was working..but for some reason it wrecked havoc with the server or the forum itself and they had to disable it as well as the function that allows you to search for members posts.