It would have to be a driver issue, but there are no XP drivers available anymore officially from EFI or Xerox.
If you can find one, reinstall it fresh. Check in Command Workstation, I would have to assume the Face-down option will be showing on the job, if you change it in Command Workstation and it works, the driver is the problem, if setting it in Command Workstation does nothing, the Fiery is the problem, reload it.
I have a EX700 with Window XP Professional, that with not print faceup when the option is selected.