Here's what SquareEnix has posted on the official playonline.com website:
From:PlayOnline
01/19/2004 07:00 [PST]
Connection Error Notice
On 1/16/2004 (PST), we have received complaints about connection errors with the game servers.
Upon investigating, we found out that there was a problem with the servers and we have since fixed the problem. We are currently monitoring the servers and working on preventing such problems from happening again.
We apologize for any inconvenience.