Details:
After gettin' into official website and not logging in, selected language by default (English UK) suddenly changed to Français and automatically logged me in, but the displayed user on the upper right corner was not correct.
I changed language back to English (UK) and got disconected, so data on the upper right corner showed normal "Log in / Register" options. I then changed language to Français once more and the issue came back, giving another logged user in return (different from the first one).
I've changed to the rest of the available languages and there was no problem at all, just Français option.

Date & Time:
Mar. 1, 2013 10:45 CET

Location:
Final Fantasy XIV: A Realm Reborn website
http://eu.finalfantasyxiv.com/

Operating System:
Windows 7 Professional

Browser:
Google Chrome 25.0.1364.97 m