Had the same issue. Installed it on a second computer at my girlfriend's house for when I was visiting, worked fine for a month and a half, then suddenly stopped, with every single other program and game working just fine. Tried various fixes, including the multi-hour reinstall process, nothing. Finally came here, read this topic, restored back to before the last Windows update, and it works again. Good, but not sure what we'll do in the future, we can't just not update Windows solely so we can play XIV. >_<

Anyway, for reference: Windows 7 64 bit, x2 2.8Ghz processor, 3 GB RAM, 5770 Radeon HD. Worked fine until around the September 28th Windows update. Tried running as Admin, compatibility, restarts, disabling antivirus, and nothing worked until we restored to before the last Windows update, always got as far as OP, then the swirl would freeze and the login refused to pop up.

Now if only we could get certain quests to work on her main computer... the L25 dungeon Company quest and some others crash on hers (as seems to be an issue a few people have reported here), been having to use the back up comp to do some things together. Square Enix really needs to get it's butt in gear, we haven't had near this many issues with other game/MMO clients, and we're well into the second year of XIV's lifecycle. -_-