A certain site had UI mods for the FFXIV UI, being just some graphical changes. If you're using one of these remove it and replace it with the original file. Apparently if the file has been modified it will cause the update installation to fail. I was using one for awhile to make the chat log easier to see and my version update kept failing. Once I changed back to the original the update succeeded and installed just fine. So just a note, if you use dat mods or any type of UI changes remove those before you update.
FINAL FANTASY XIV Roleplayer
Sair Gammonari - Hyur Midlander Male - Conjurer (Somewhat retired.)
Mihana Zhralyia - Miqo'te Seeker of the Sun Female - Archer