There is a script in the default scripts folder with Quark which does what my script does (I never noticed it, just used my own!). It causes Quark to quit too, presumably when it comes to the 'set story' bit.
When I open that script in Script Editor, there is a bit of a clue, as one line reads:
set «class STDR» of story 1 of nameBox to false
I wonder which property that should be?