[Dovecot] Dovecot dying when deliver is called

[MyGoddess]

Hello,
 
I run a debian etch server with the mail services configured like their: http://workaround.org/articles/ispmail-etch/
It worked during month but of the last upgrade it doesn't work anymore when postfix calls deliver.
dovecot version is 1.0.rc15. I don't remember which was the previous version.
 
There is no error accessing dovecot in any other way.
 
Here my configuration:
# /etc/dovecot/dovecot.conf
log_path: /var/log/dovecot_err.log
info_log_path: /var/log/dovecot.log
log_timestamp: %Y-%m-%d %H:%M:%S
protocols: pop3 pop3s imap imaps
login_dir: /var/run/dovecot/login
login_executable(default): /usr/lib/dovecot/imap-login
login_executable(imap): /usr/lib/dovecot/imap-login
login_executable(pop3): /usr/lib/dovecot/pop3-login
mail_privileged_group: mail
mail_location: maildir:/home/vmail/%d/%n
mail_debug: yes
mail_drop_priv_before_exec: yes
mail_executable(default): /usr/lib/dovecot/imap
mail_executable(imap): /usr/lib/dovecot/imap
mail_executable(pop3): /usr/lib/dovecot/pop3
mail_plugin_dir(default): /usr/lib/dovecot/modules/imap
mail_plugin_dir(imap): /usr/lib/dovecot/modules/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/modules/pop3
pop3_uidl_format(default):
pop3_uidl_format(imap):You can find a copy of the 
pop3_uidl_format(pop3): %08Xu%08Xv
auth default:
  mechanisms: plain login
  passdb:
    driver: sql
    args: /etc/dovecot/dovecot-sql.conf
  userdb:
    driver: passwd
  userdb:
    driver: static
    args: uid=1004 gid=1005 home=/home/vmail/%d/%n allow_all_users=yes
  socket:
    type: listen
    client:
      path: /var/spool/postfix/private/auth
      mode: 432
      user: postfix
      group: postfix
    master:
      path: /var/run/dovecot/auth-master
      mode: 384
      user: vmail

I am not able to get a coredump.
 
You can find a copy of the error mail attached. I didn't get any message from log files.
 
If someone have any clue, I will helping.
 
Regards,
Pierrick Caillon
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