I have noticed something now on the forum, and that is something in the translation, not only in English, but in every single translation that exists of YaBBSE or Simple Machines.
Users should be Members in the Users online section. Or else the Guests are not users and Users are Users twice.
I've changed the string in my YSE translation to Member(s). Maybe you can change it to Members. Don't want to have this bogus translation bug into Beta and in the future. ;)