This POL-1158 error message is a result of the Steam version of FINAL FANTASY XI not being uninstalled correctly. The “ffxi” directory is not uninstalled when you select “Delete Local Content” from Steam. This is prohibiting the PlayOnline Viewer and FINAL FANTASY XI from updating if you reinstall the PlayOnline Viewer and FINAL FANTASY XI through Steam. This issue affects all Windows platforms.

To resolve the issue, please follow these steps:
 1) Uninstall FINAL FANTASY XI from Steam using the "Delete Local Content" option, then close Steam.
 2) Before reinstalling PlayOnline Viewer and FINAL FANTASY XI from Steam go to: C: → Program Files (x86) → Steam → steamapps → common
 3) Delete the “ffxi” directory
 4) Start Steam
 5) Reinstall the PlayOnline Viewer and FINAL FANTASY XI

If you continue to have issues, please completely uninstall FINAL FANTASY XI from Steam and install the standalone Windows version from the following page: http://www.playonline.com/ff11us/download/media/install_win.html