I just went to the board index, and scrolled all the way down to the bottom, and this is what I saw:
Click to view attachment
Only two users. And 27 guests.

Wha- ???
What is going on here? I refreshed the page, and it was the same. But when I clicked my shortcut to MSFN, it was all back to normal. 543 guests and 49 users. Huh? Something weird is going on here. Admins, have you been messing around with things again? Or did you all log off to have a quick coffee break and come back at the same time?

That's not forum index, that's topic index in your screenshot.

No, it's not. I cut the screenshot so it wouldn't be as big. It was the main index page, at the bottom. I would show you the whole screenshot, but I deleted it. I am absolutely positive it was the forum index.

You can sometimes see this behavior after a server restart or an apache restart. The forums will see everyone as logged out after the restart until people start moving around again.

OK, whatever. It hasn't happened again, so I guess I won't worry.