I think there might be something screwy with the cache settings in vBulletin. It does some weird stuff, like I will hit "new posts" and have no new posts. I can do that for anywhere from 5 to 20 minutes, and sometimes new posts come up even though the forum software says the search was performed 20 minutes ago. Also, sometimes after logging in the login box still shows that you need to log in where it normally displays "Welcome, <member>". If I go to another page, the login prompt goes away and my username comes back. It's just odd behavior, and I wonder if you might have a setting somewhere that holds the pages in the server cache for too long.
Just a thought. It would explain why it shows so many registered members on for so long with no posts. It could be showing them as still online long after they have left.
Just a thought. It would explain why it shows so many registered members on for so long with no posts. It could be showing them as still online long after they have left.