You must select the top-level element for insert replace or insertbefore
in my example the xml is like this:
<Root><RTF/></Root>
Your error is because you try to insert not in the good place or if you try to insert an element that don't has the correct name!
your error message is You can't insert testo1 in modello because your schema don't allow this!!!
What you try to make is:
<Modello><testo1/><Modello>
Infopath 2007, Langage: C#2.0 (Modèle Objet 2003)
merci de lire ceci