Problem in emacs lily mode on mac x

[libero . mureddu3]

Hi!
I started to use Aquamacs to edit my .ly files, it is a carbon emacs particulary
well working with mac os x. I never had problems before, but installing the
new version of this emacs (0.9.4 based on Emacs 22.0.50.1), it doesn't load
the lily mode and I receive the following error message: Wrong type argument:
arrayp, 0
I'm not able to debug elisp, can you help me to understand what's wrong?
There was a message on the list about the same problem and the solution was
to load the lily mode manually but in this case I obtain the same error as
above.
I use lilypond.app 2.6.1-1
mac os x 10.3.9
Ibook g4
Thank you
Libero Mureddu

Emacs backtrace:
Debugger entered--Lisp error: (wrong-type-argument arrayp 0)
  substring(0 0 -12)
  (string-to-number (substring (count-midi-words) 0 -12))
  (let ((fnameprefix ...) (allcount ...) (count ...)) (concat fnameprefix
(if ... ...) ".midi"))
  LilyPond-string-current-midi()
  (concat LilyPond-midi-command " " (LilyPond-string-current-midi))
  (list "Midi" (concat LilyPond-midi-command " " 
(LilyPond-string-current-midi)))
  (list (backquote-list* "LilyPond" (concat LilyPond-lilypond-command " %s")
(quote ...)) (quote ("TeX" "tex '\\nonstopmode\\input %t'" "%t" "%d" "ViewDVI"))
(backquote-list* "2Dvi" (concat LilyPond-lilypond-command " -b tex %s") (quote
...)) (backquote-list* "2PS" (concat LilyPond-lilypond-command " -f ps %s")
(quote ...)) (list "2Gnome" (concat LilyPond-lilypond-command " -b gnome
%s")) (quote ("Book" "lilypond-book %x" "%x" "%l" "LaTeX")) (quote ("LaTeX"
"latex '\\nonstopmode\\input %l'" "%l" "%d" "ViewDVI")) (list "View" (concat
LilyPond-pdf-command " %f")) (list "ViewPDF" (concat LilyPond-pdf-command
" %f")) (list "ViewDVI" (concat LilyPond-dvi-command " %d")) (list "ViewPS"
(concat LilyPond-ps-command " %p")) (list "Midi" (concat LilyPond-midi-command
" " ...)) (list "MidiAll" (concat LilyPond-all-midi-command " " ...)))
  (\` (("LilyPond" ... "%s" "%l" "View") ("TeX" "tex '\\nonstopmode\\input
%t'" "%t" "%d" "ViewDVI") ("2Dvi" ... "%s" "%d" "LaTeX") ("2PS" ... "%s"
"%p" "ViewPS") ("2Gnome" ...) ("Book" "lilypond-book %x" "%x" "%l" "LaTeX")
("LaTeX" "latex '\\nonstopmode\\input %l'" "%l" "%d" "ViewDVI") ("View" ...)
("ViewPDF" ...) ("ViewDVI" ...) ("ViewPS" ...) ("Midi" ...) ("MidiAll" ...)))
  eval((\` (("LilyPond" ... "%s" "%l" "View") ("TeX" "tex '\\nonstopmode\\input
%t'" "%t" "%d" "ViewDVI") ("2Dvi" ... "%s" "%d" "LaTeX") ("2PS" ... "%s"
"%p" "ViewPS") ("2Gnome" ...) ("Book" "lilypond-book %x" "%x" "%l" "LaTeX")
("LaTeX" "latex '\\nonstopmode\\input %l'" "%l" "%d" "ViewDVI") ("View" ...)
("ViewPDF" ...) ("ViewDVI" ...) ("ViewPS" ...) ("Midi" ...) ("MidiAll" ...))))
  custom-initialize-reset(LilyPond-command-alist (\` (("LilyPond" ... "%s"
"%l" "View") ("TeX" "tex '\\nonstopmode\\input %t'" "%t" "%d" "ViewDVI")
("2Dvi" ... "%s" "%d" "LaTeX") ("2PS" ... "%s" "%p" "ViewPS") ("2Gnome" ...)
("Book" "lilypond-book %x" "%x" "%l" "LaTeX") ("LaTeX" "latex 
'\\nonstopmode\\input
%l'" "%l" "%d" "ViewDVI") ("View" ...) ("ViewPDF" ...) ("ViewDVI" ...) ("ViewPS"
...) ("Midi" ...) ("MidiAll" ...))))
  custom-declare-variable(LilyPond-command-alist (\` (("LilyPond" ... "%s"
"%l" "View") ("TeX" "tex '\\nonstopmode\\input %t'" "%t" "%d" "ViewDVI")
("2Dvi" ... "%s" "%d" "LaTeX") ("2PS" ... "%s" "%p" "ViewPS") ("2Gnome" ...)
("Book" "lilypond-book %x" "%x" "%l" "LaTeX") ("LaTeX" "latex 
'\\nonstopmode\\input
%l'" "%l" "%d" "ViewDVI") ("View" ...) ("ViewPDF" ...) ("ViewDVI" ...) ("ViewPS"
...) ("Midi" ...) ("MidiAll" ...))) "AList of commands to execute on the
current document.\n\nThe key is the name of the command as it will be presented
to the\nuser, the value is a cons of the command string handed to the 
shell\nafter
being expanded, and the next command to be executed upon\nsuccess.  The 
expansion
is done using the information found in\nLilyPond-expand-list.\n" :group LilyPond
:type (repeat (cons :tag "Command Item" (string :tag "Key") (cons :tag "How"
... ...))))
  (defcustom LilyPond-command-alist (\` (... ... ... ... ... ... ... ...
... ... ... ... ...)) "AList of commands to execute on the current 
document.\n\nThe
key is the name of the command as it will be presented to the\nuser, the
value is a cons of the command string handed to the shell\nafter being expanded,
and the next command to be executed upon\nsuccess.  The expansion is done
using the information found in\nLilyPond-expand-list.\n" :group (quote LilyPond)
:type (quote (repeat ...)))
  eval-buffer(#<buffer  *load*> nil "lilypond-mode" nil t)
  ;;; Reading at buffer position 16095
  
load-with-code-conversion("/Volumes/scripta/Users/libe/site-lisp/lilypond-mode.el"
"lilypond-mode" nil nil)
  execute-extended-command(nil)
  call-interactively(execute-extended-command)