I'm having the same problem, I rolled back from Windows 8.1 to Windows 7 (Windows 8.1 was killing my SSD, literally, kept screwing with the Master Boot Record and crashing my system) and I can't seem to reinstall Final Fantasy XVI, first I had about 10 client crashes... then I'm having the patch error.

The game itself is already starting to bore me, having a bad launcher is not helping.