Just a quick note if there are other Mac OS X Leopard users out there with Kyocera Mita printers: the installer installs the PPD files with a different strategy than what 10.5 expects, as the language subdirectories aren’t present now by default, and the installer creates them without permissions to execute (enter) them.
The easy fix is to open a terminal and run this command:
chmod +x /Library/Printers/PPDs/Contents/Resources/*.lproj
This now allows the setup utility to detect the PPDs again, and fixed the problem for me.