PC Windows 10
Wired Connection
Typically have Firefox or Chrome active, Discord. Other than that, I turn everything else off.

I've done the following fixes:

http://forum.square-enix.com/ffxiv/threads/328316-Error-11018-FFXIV-Boot-Error-File-access-failed-during-version-check...

https://www.reddit.com/r/ffxiv/comments/2es6tb/possible_solution_for_error_11018_file_access/

Also uninstalled the game and used CCleaner to remove all left over parts of the game from my system.