PPD files not found

[Occam]

First - 'standard' printing works ok.
But - I cannot use any special capabilities of the printer, since the PPD files (properly placed and named, by CUPS, in /etc/cups/ppd/) cannot be found!
lpoptions -l tells me "Destination Kyocera has no PPD file!"
CUPS at localhost:631 works ok - except for "Configure printer" which gives an Error: server-internal-error

I am running CUPS 1.1.20 supported by ESP Ghostscript 7.07.1, under Slackware 10 using kernel 2.6.7, normally with KDE 3.2.3 as desktop.