dovecot - Feb 2012 - locking problem

I have one user who can't read his e-mail. The /var/log/mail.log file  
has this statement.

dovecot: IMAP(<user>): Timeout while waiting for lock for transaction  
log file /users/<user>/mail/.imap/INBOX/dovecot.index.log

I tried killing the imap daemons and removing the lock file,
but it keeps coming back. Any idea what else to do?

This is the dovecot file:

dovecot -n
# 1.2.9: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-28-server x86_64 Ubuntu 10.04.3 LTS
log_timestamp: %Y-%m-%d %H:%M:%S
protocols: imap imaps pop3 pop3s
ssl_cert_file: /etc/ssl/certs/ssl-cert-snakeoil.pem
ssl_key_file: /etc/ssl/private/ssl-cert-snakeoil.key
disable_plaintext_auth: no
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: mbox:~/mail:INBOX=/var/mail/%u
mbox_write_locks: fcntl dotlock
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
auth default:
  mechanisms: plain login
  passdb:
    driver: pam
  userdb:
    driver: passwd
  socket:
    type: listen
    client:
      path: /var/spool/postfix/private/auth-client
      mode: 432
      user: postfix
      group: postfix

--myron
================================Myron Kowalski
MoCoSIN Network/Systems Administrator
Moravian College
myron at moravian.edu
(610) 861-1441

On 1.2.2012, at 16.09, myron wrote:
> I have one user who can't read his e-mail. The /var/log/mail.log file
has this statement.
> 
> dovecot: IMAP(<user>): Timeout while waiting for lock for transaction
log file /users/<user>/mail/.imap/INBOX/dovecot.index.log
> 
> I tried killing the imap daemons and removing the lock file,
> but it keeps coming back. Any idea what else to do?
..
> mail_location: mbox:~/mail:INBOX=/var/mail/%u
How large is the /var/mail/<user> mbox file?