could have some ntfs errors preventing it from updating a file. Try running a chkdsk until it doesn't find any errors, then try again (chkdsk c: /P or chkdsk c: /F is fastest, usually just finds/fixes file system errors--using /R (sector recovery option)will check integrity of every sector and takes a long time to finish). If it is still tanking, try to catch which file it is erroring on and try to rename that file (something like ffximain.dl_ so it's easy to rename it back if renaming it fails)--might get lucky and it downloads a fresh copy of it.
Using chkdsk in XP: http://support.microsoft.com/kb/315265
Using checkdisk in Vista/7: http://www.howtogeek.com/howto/windows-vista/guide-to-using-check-disk-in-windows-vista/
Worst case scenario, you could try one of the .rar packages some users had posted for the last update for maunually updating the rom/dat files. It worked fine for my US install: http://www.bluegartr.com/threads/101113-Direct-link-to-12-6-update-files
Raist
Edited, Jan 4th 2011 7:02pm by BDHERTZER