Patcher Error.

[Grit]

Typically error 20524 means that the patcher found something wrong with your files, and the update will not continue. This could mean that something became corrupt, or you're missing an older patch that it needs in order to apply the new one.

Some people have fixed this by changing the date on their game.ver file to go back and look for older files, or by deleting their FFXIV downloads folder under My documents > My Games

Still, a complete re-install is probably the recommended treatment. Take note that your local FFXIV folder (under my documents) is static and will not be deleted when you uninstall, so if a re-install does not resolve your issue, the next step will be to delete certain parts of that folder.. or the entire thing. You will lose UI settings and saved character models, but oh well.

:Edit:

You can avoid losing any of your data by backing up your folder (Copy - Paste). If a deletion of the original folder does not resolve the issue, return the back-up folder to where it belongs.