Indesign script doesn't work anymore after saving without any change

Two months ago I wrote a script which worked very well.
Now I had to change just the name of the character style and after saving, the script is not able to define the variable k anymore. The original script is still working and when i make a duplicate in the Finder, this works too. When I save a copy from the editor it also works. But as soon as I save it after making a single change in the script, even just the removal of an extra return at the end of the script, so the content was’nt really changed, the script doesn’t work anymore.

Applescript Runtime Error
Can’t get k of {text from character 11 to character 44 of story id 6372 of document “EMMmargewoordWeg.indd”, text from character 594…etc, etc,…}

In Script Debugger I can see that foundText is set to the list you see in the error, and lastitem is set to 45
but k remains undefined

I’m working on Max OS 10.6.5 intel with Indesign CS3 latest update
Indesign was not updated since the making of the first script
Below you find the original script

Anyone, any ideas?

tell application "Adobe InDesign CS3"
	set find text preferences to nothing
	set change text preferences to nothing
	set find what of find text preferences to ""
	set properties of find text preferences to {applied character style:"Margewoord"}
	set properties of change text preferences to {applied character style:"Margewoord-done"}
	tell document 1
		find text
		set foundText to result
		--display dialog foundText
		set lastitem to (count of result)
		repeat with k from lastitem to 1 by -1
			set the selection to item k of foundText
			set mySelection to the selection
			--display dialog mySelection as text
			set myParagraph to mySelection's items as text
			--display dialog myParagraph as text
			tell (first insertion point) of selection
				make new text frame with properties {geometric bounds:{0, 0, 15, 25}, contents:myParagraph, applied object style:"MargeObjectstijl"}
			end tell
			-- 				set contents of (first insertion point of selection) to return
		end repeat
		change text
	end tell
end tell

That sounds a bit like a terminology conflict. Have you added any scripting additions or InDesign plug-ins? What happens if you change to Show Raw Syntax and back?

No, I haven’t installed any plugins for Indesign or scripting addons. I’ve tested the script also on some other macs in the department with the same results.
And also the switching to raw and back doesn’t make any difference