insert-at-cursor doesn't work

[Marco Terzuoli]

Hi,
I have created a window and placed a gtk.Entry inside it. I would like to
perform some tasks when the text of the entry is changed, so I have created
a connection such as this:

self.name_text=gtk.Entry()
self.name_text.connect("insert-at-cursor",self.name_text_changed,None)

Also, I have defined the function name_text_changed as follows:

def testo_cambiato(self,entry,string,data=None):

I don't receive any error while the program is run, but actually nothing
works.... I have tried to deal with other signals concerning the entry such
as activate and delete-from-cursor and they worked perfecly, so I just
don't understand what's wrong with my code.
Can anybody help?
Thanks
Marco