When you open the game, and log in, and hit play and windows instantly tells you "Final fantasy 14 has encountered an error and needs to close"
I spent 5 hours on this and i work IT and had tried everything i knew to do before finally finding out what was wrong.

Some of the problems could be if you have an ATI card, but i have nvidia.

Log in to the main site at https://membership.square-enix.com/users/sign_in
(or just go to the site on your own if you don't trust my link)

When i logged in there it said my account had possibly vandalized and i had to change my password, and then when i logged back into the game it made me re enter my product code.. but after that, it worked.

It's very odd that something not right with a username/password could cause an application to crash constantly, but it happened. and i just wanted to share that with anyone else having this trouble since you can't get to a support rep.