lilypond-book problem 2.5.30

[libero . mureddu3]

Hi,
after a crash of two months of my laptop, I am very happy to use again lilypond!
And congratulation for the new installer, it is really easy and nice to install
and use!

I've just tried to use lilypond-book in 2.5.30 on mac os x 10.3.9, but I've
received the following error:

Computer-di-Libero-Mureddu:~/Desktop liberomureddu$ 
/Applications/LilyPond.app/Contents/Resources/bin/lilypond-book
--output=~/Desktop  prova.tex
Traceback (most recent call last):
  File "/Applications/LilyPond.app/Contents/Resources/bin/lilypond-book",
line 60, in ?
    import lilylib as ly
ImportError: No module named lilylib

The file I used is from the manual:

\documentclass[]{article}
\begin{document}
Normal LaTeX text.
\begin{lilypond}
\relative c?? { a4 b c d }
\end{lilypond}
 More LaTeX text.
\begin{lilypond}
\relative c?? { d4 c b a }
\end{lilypond}
\end{document}

Thanks again for your great job!!!

Libero Mureddu