QTR-Quadtone RIP

Hello. I have been using QTR for some years now, mainly for printing dig negs. For other reasons, on the iMac I use for printing I still have OSX 10.6.8 (i.e. Snow Leopard)

my current setup is a 4800 with oem inks.

I am experiencing more and more often the following problem:

the Quad4800 printer is still present in the system, but sometimes, when I choose to print, no quadtonerip settings are available anymore. Thus, by looking on the printer settings and opening the queue, the "driver version:" field is blank and it does not come back even if I choose it manually. Obviously, all the page setup options are missing and only "element1" appears in the page format field in the printing dialog box

the only option I found is to remove QTR, all the files in the Library folder, reinstall it from scratch and reinstall the printer and the custom curves I have. This way the setup lasts like three days

does anybody experienced something alike?

Thanks a lot for any help

simone

addition: by looking at the error messages in the console, I found that the link to the driver ceases to exist when a curve is dropped in the drop-quad-profile app.

this is the error reported by the console:
18/06/15 07.52.01 [0x0-0x32032].com.yourcompany.DropScript /Applications/QuadToneRIP/CurveDesign/Drop-Quad-Profile.app/Contents/Resources/script: line 20: -z: command not found

something is wrong with the underlined line (20) in the script

quadprofile "$1" >"$TEMP" 2>&1
if ! -z "$TEMP"
then
open -e "$TEMP"
(sleep 3; rm -f "$TEMP") &
fi

then, when trying to print, CS3 gives this message:
17/06/15 23.10.27 Adobe Photoshop CS3[537] InkChecker could not get ppd for Quad4800