Perhaps he tried to login, but didn't write the password right, but wrote the username right. I don't know if the member, in that case, is appeared in the "Who's online", but if it does, that's the reason.
Also, I noticed that one guest is doing an unknown action. Weird. I still don't know how guests can do nothing or nothing members can see.
I think it is a date bug. Y2K+12 arrived! 

Y2K+12? Do you mean the following?
Y2K+12 = Year 2x1000+12 = Year 2012
But, 2012 arrived 8 months and 16 days (and some hours) ago! What did you mean?
What does that have to do withdate bugs?
Oh, and I think that guest is still logging into the forum, and time and date are still the same!
