No one has reported this problem before and I haven't seen it on any sites.
My guess is that you are using the Access version of the forum, which it is recommended that keep the active users page disabled from the admin area.
The reason for this is that Access never totally delets items till you download and compact and repair the database so the table just grows and grows slowing down your forum until the database finally becomes corrupted and crashes your entire forum.
What you need to do is download the access database and open it in access and select comapct and repair database from the tools menu.