We've had a maddening problem with some machines since we rolled out XP Sp3.

All machines that had Canon CLC 4000 (Fiery Z7100 rip) and CLC 5100
(Fiery Z7500 rip), have lost the ability to duplex.

You can go in set the options such as duplex, paper size, orientation
etc, but duplex would immediately revert back to off the moment you
clicked ok. Deleting/reinstalling the printer had no effect.

Apparently something has changed in the way windows stores driver
profiles in XP SP3. I deleted the old driver profiles, and recreated
them from a machine that had SP3 installed, and then associated them
with the printers again.

Reinstalling the printers with the new profiles fixes the issue.

That's a chunk of my life I'll never get back as the only thing I could
find searching the web was another poster having the same problem.

Hope it saves somebody some time. So far I don't see the issue with
other copiers/printers that I have profiles for, but perhaps it just
hasn't been reported.