My first guess would be that the patch file didn't properly download and that you should redownload the patch. There are a couple of options for doing this, some of which you may already be familiar with.

This first is to navigate to the patch folder, typically C:\Users\[putYourWindowsUserNameHere]\Documents\My Games\FINAL FANTASY XIV\downloads\ffxiv\48eca647\patch, then delete D2011.12.14.0000.patch. When you restart the client it will begin downloading again.

The second is to use the .torrent file in the nearby metainfo folder to download the patch with a BitTorrent client. After it finishes (15min or so), just copy and paste the downloaded .patch file to the patch directory, overwriting the file that's there, and launch the client again.

I hope some of that information is new and helpful.