[Dovecot] fstat() failed with file */dovecot.index.log

[Nicolás]

Hi list!

I'm using Dovecot along with Postfix (with MySQL) and I'm having some 
curious error messages in the mail log. Everything runs normally and 
suddenly I start viewing messages like these:

Oct 12 14:24:23  dovecot: last message repeated 5 times
Oct 12 14:25:23  dovecot: last message repeated 6 times
Oct 12 14:26:23  dovecot: last message repeated 6 times
Oct 12 14:27:23  dovecot: last message repeated 6 times
Oct 12 14:29:22 mail dovecot: imap(nicolas at devels.es): Error: fstat() 
failed with file 
/home/vmail/devels.es/nicolas/Maildir/dovecot.index.log: No such file or 
directory
Oct 12 14:30:23  dovecot: last message repeated 5 times
Oct 12 14:31:23  dovecot: last message repeated 6 times
Oct 12 14:33:22 mail dovecot: imap(nicolas at devels.es): Error: fstat() 
failed with file 
/home/vmail/devels.es/nicolas/Maildir/dovecot.index.log: No such file or 
directory
Oct 12 14:34:23  dovecot: last message repeated 5 times
Oct 12 14:35:23  dovecot: last message repeated 6 times
Oct 12 14:36:01 mail dovecot: imap(nicolas at devels.es): Error: fstat() 
failed with file 
/home/vmail/devels.es/nicolas/Maildir/dovecot.index.log: No such file or 
directory

This file which Dovecot references to indeed exists, is accesible, etc. 
Once I get the first of these messages, the user stops receiving e-mails 
(the mail server keeps receiving them normally, though) until he 
restarts the mail client. Then the error msg is gone and he receives all 
their unreceived messages. This error appears in 6-12h. intervals once 
the user starts their client.

Version is 2.0.19, and dovecot -n is:

root at mail:~# dovecot -n
# 2.0.19: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-32-generic-pae i686 Ubuntu 12.04.1 LTS ext4
disable_plaintext_auth = no
log_timestamp = "%Y-%m-%d %H:%M:%S "
mail_location = maildir:/home/vmail/%d/%n/Maildir
mailbox_idle_check_interval = 2 mins
namespace {
   inbox = yes
   location =
   prefix = INBOX.
   separator = .
   type = private
}
passdb {
   args = /etc/dovecot/dovecot-sql.conf
   driver = sql
}
protocols = imap pop3
service auth {
   unix_listener /var/spool/postfix/private/auth {
     group = postfix
     mode = 0660
     user = postfix
   }
   unix_listener auth-master {
     mode = 0600
     user = vmail
   }
   user = root
}
ssl_cert = </etc/ssl/certs/dovecot.pem
ssl_key = </etc/ssl/private/dovecot.pem
userdb {
   args = uid=5000 gid=5000 home=/home/vmail/%d/%n allow_all_users=yes
   driver = static
}
protocol lda {
   auth_socket_path = /var/run/dovecot/auth-master
   log_path = /home/vmail/dovecot-deliver.log
   postmaster_address = postmaster at devels.es
}
protocol pop3 {
   pop3_uidl_format = %08Xu%08Xv
}

Thanks so much for any help!

Nicolás