Ok i'm sure everyone else is SICK of seeing the same topics over and over asking the same question about the same error so i've composed a quick guide to help out *_* If you get any other errors let me know. Most just involve firewalls.
I am NOT an admin or moderator i'm just a normal member who's had all of the following errors and managed to find a solution. I will not be covering errors that arnt numbered such as being unable to move or type.
Note: The dreaded 903 is still effecting players now. There is a topic covering the 903 error here: http://boards.sega.com/psobb/viewtopic.php?t=1841
Incorrect Username and/or password.
Check your password and username to see if they're correct. If you can connect to the billing site but not PSO just change your password. If using a JP account make sure to remove the J before the username and password in the confirmation email. Make sure your account is actually ACTIVATED before you try log in -_-;
Patch server connection failed
The patch server is currently under mainternance as explained or you may be suffering difficulties through your firewall and/or router. Remove the router and disable the firewall and try reconnect.
Mainternance will be every Thursday to my knowledge.
This program has not been updated
Run the patch download. If it says no patches are avaliable restart the program. If this continues re-install PSO but check first to see if other people are having the same problem at the same time. It may be a problem with the server.
Your patch download may have been corrupted. Disable firewalls before patching in the future.
Failed to update to Gameguard Server Update Server
Turn of your firewall and restart the program. If problems persist the server may be down. Try again an hour or so later (not every 5 minutes) if problems persist follow the same technique used in 903. Remove and routers and/or firewalls.
If that fails create a new windows account (Control panel > User Accounts) and it should work then. Thanks to Azusa for finding this fix ^_^ it's been confirmed to work.
Failed to Update Files
Again it's firewall. Try again and if it still fails re-install PSO and re-patch. It may be a problem with the patch server so try again later if you dont want to re-install. Make sure the patch client is using the right directory for your game client.
Game already has gameguard running on it
Turn off your firewall and restart PSO. If problems persist restart your computer and try again. It may also be a server error.
Unable to connect to DNS server
Try again later on. If your using an internet provider that uses a proxy server it's probebly preventing you from connecting (AOL for example)
GameGuard Update removed
Do as it says and check your internet settings, re-route your firewall to allow scripts through (just disable it!) Also try re-starting your computer. It may be a problem with your internet connection which point i cant help you. If your using a broadband modem unplug it and try again (usually works for me when i cant connect to something) but just mess around with the way your internet works.
This also appears when you click the cancel button when the gameguard updater is starting up.
Gameguard runtime error
Re-download a new version of PSO from either the website (when released) or fileplanet. Re-install the files. DO NOT use a download accelerator on the download it's known for corrupting data packages.
The server is full
Try connect again after 10 minutes and then if it continues try an hour later. If you STILL cant get on check the forums it may be a bug on the server if numerous people are reporting it. The more people trying to connect to the server at the same time the less likely you are to get on.
There are 7 ships, 9 blocks on each with 100 players per block. Do the math. 6300 people total. There are over 10,000 people with a game client and rising.
Third Party Software - Hacks
If your not using any third party or hacking tools to play PSO simply press ctrl+alt+delete on your keyboard and end process for any programs under your windows account name (not SYSTEM, LOCAL SERVICE or NETWORK SERVICE) this will close any programs running that the game may consider third party.
The motto is: BE PATIENT!
(Yay my 100th post is usefull!)