Hopefullly someone in Technical Support is actually reading these or at least a moderator is bringing this to their attention.
I do not know about the rest of the people that have reported here but the sequence of events I have experienced are as follows:

- Launcher start-up: normal
- Log-in: successful
- Update to version 2.51: successful, no complications. Launcher restarts as per usual.
- Successful start-up of game-client
- Attempt to Connect to Data Center / World content: Failed ; error [2002] ; game-client disconnects and shuts down. All FFXIV:ARR processes stop.
- User restart of Launcher: successful
- Log-in to Launcher and Game-client: successful and normal
- Attempt to Connect to Data Center / World content: Failed ; error [2002]

I and others may have been continuously hitting this wall for several hours now with no word on whether or not ANYONE at Square-Enix has even acknowledged the problem.
The previous issue that it seems you have fixed seemed to be similar to this. However, the issue that you fixed was where people who failed to connect to their Data-Center/World were unable to log back into the game. That does not seem to be the issue here.
What does appear to be the issue is that players are unable to get into their Data-Centers/Worlds at all. We keep getting disconnected ( error 2002) on each attempt.

If it does matter at all to someone in Technical Support, or even to this situation, I know that I did not log-out my character prior to last night's maintenance. I was in an instance when it began and was subsequently disconnected. And from another Tech. Support thread it seems you (Square-Enix) are also having trouble with the Instance Servers.

If there is any information that your technicians require I am sure the people reporting this problem (and others of course) will be willing to provide them.
Here's hoping that you can get this issue fixed!