Database connection lost? Most likely.
I mean that server lost connection with mysql. It always happened on my server when I had no optimized mysql database and had same symptoms as you got. What happens with peoples that are inside game? Do they got freeze or they can normally play, their characters are saved but just new players can't login?
I guess the server lost connection with mysql. People were able to play but couldn't login again.
Bingo!
hosting on own computer?
Nope, Dedicated
Ur hosting on cheapvps?
becouse i have the same problem there on 8~ server lost connection
Bring this up!