NSReceiverEvaluationScriptError: 4(1) ????????

I’ve looked around this site and found that it is a general applescript error, with no specific solution.
I’ve placed the effected part of the script below.
Using Xcode I using radio buttons on a preferance window. so when it is open the button will reflect the defaulted selection.
if DPrinter = “Ding” then
tell application “Printer Setup Utility”
set current printer to printer “Printer 1”
end tell
set content of text field “Activep” of window “window 1” to “Printer 1”
end if
set the state of cell “Ding” of matrix “area” of window “Preferences” to 1

this works but if I try and set the other cell titles to activate (tested each one on its own) I get that error.
I’ve copied the titles into the parts of the script, so I don’t think mis-typed titles are the problem, and I didn’t (need) to change anything else.

Can anyony give me a hand