I've got a Xerox WorkCentre Pro C3545 and the Xerox Snow Leopard driver I downloaded and installed from the Xerox site DOES NOT WORK AT ALL. If I add the printer in Snow Leopard the Add Printer window never detects the proper model and uses Generic Postscript Printer. If I then force it to use the WCP3545 driver it then complains that not all of the software is installed. At this point any application I tell to use the WCP3545 printer queue attempts to print and immediately errors in the queue.
I have also trying resetting the printer subsystem, this did not change anything.
I have also tried the /Library/Printers permissions fix, and this did not change anything.
This worked just fine when I was still running 10.5. After the upgrade to 10.6 it has never worked using the Xerox driver, only using the Generic Postscript Driver which does not expose features I need access to on the device.