Grazie ancora Enrico, ho riletto la guida e ho trovato alla sezione 2.6 quello che mi hai detto:
Note that you must treat lstlisting environments exactly the same way as you would treat verbatim environments. When using \defverbatim that contains a colored lstlisting, use the colored option of \defverbatim.
Aggiungo che nella sezione 3.13 dove si parla del testo in verbatim si dice:
One another frame, Euclid would like to show a listing of an algorithm his friend Eratosthenes has send him (saying he came up with it while reorganizing his sieve collection). Euclid normally uses the verbatim environment and sometimes also similar environments like lstlisting to typeset listings. He can also use them in beamer, but he must add the fragile option to the frame.
D’ora in poi me lo ricorderò.
Grazie Alberto