[Dovecot] Error 89

[Hodges]

Just installed dovecot 1.1.2. downloaded from dovecot.org. Seemed to 
compile and install OK but I get the following error when I try to start it
"child 28410 (auth) returned error 89 (fatal failure)"
I just want to use it for SMTP/SASL authorization, not Pop3 or IMAP, as yet
It looks as though I haven't installed some component or other but what?
Config file follows;

# 1.1.2: /usr/local/etc/dovecot.conf
protocols: none
login_dir: /usr/local/var/run/dovecot/login
login_executable: /usr/local/libexec/dovecot/imap-login
auth default:
   mechanisms: plain login
   passdb:
     driver: pam
   userdb:
     driver: passwd
   socket:
     type: listen
     client:
       path: /var/spool/postfix/private/auth
       mode: 432
       user: postfix
       group: postfix



Steve