[Dovecot] assertion failed

[Adrian Stoica]

What is this ?

dovecot: Apr 24 13:03:29 Error: IMAP(tina.burdujan): file 
maildir-sync.c: line 1075 (maildir_sync_index): assertion failed: (uid 
 >prev_uid)

dovecot: Apr 24 13:03:29 Error: IMAP(tina.burdujan): Raw backtrace: 
/usr/libexec/dovecot/imap [0x80b8741] -> /usr/libexec/dovecot/imap 
[0x80b819c] -> /usr/libexec/dovecot/imap(maildir_sync_index+0x898) 
[0x80695f8] -> /usr/libexec/dovecot/imap [0x80698b3] -> 
/usr/libexec/dovecot/imap(maildir_
storage_sync_init+0x49) [0x8069aa9] -> 
/usr/libexec/dovecot/imap(imap_sync_init+0x40) [0x8062620] -> 
/usr/libexec/dovecot/imap(cmd_sync+0x71) [0x8
062b81] -> /usr/libexec/dovecot/imap(cmd_noop+0x26) [0x8059c76] -> 
/usr/libexec/dovecot/imap [0x805be7f] -> /usr/libexec/dovecot/imap 
[0x805bf20]
-> /usr/libexec/dovecot/imap(_client_input+0x6c) [0x805c0fc] -> 
/usr/libexec/dovecot/imap(io_loop_handler_run+0xff) [0x80bef6f] -> 
/usr/libexec/do
vecot/imap(io_loop_run+0x36) [0x80be366] -> 
/usr/libexec/dovecot/imap(main+0x46c) [0x806448c] -> 
/lib/libc.so.6(__libc_start_main+0xb9) [0xb7eb4e1
9] -> /usr/libexec/dovecot/imap [0x80568b1]

dovecot: Apr 24 13:03:29 Error: child 25748 (imap) killed with signal 6


My conf is:
exim + dovecot + mysql
exim deliver mail to maildir , because i don't know how to use LDA from 
dovecot.
the maildirs are very large, for one account could be 30000 mails.
dovecot is version 1.0.0
dovecot -n shows:
# /etc/dovecot.conf
base_dir: /var/run/dovecot/login
log_path: /var/log/mail.log
login_dir: /var/run/dovecot
login_executable: /usr/libexec/dovecot/imap-login
login_process_per_connection: no
login_process_size: 80
login_processes_count: 10
login_max_processes_count: 50
login_max_connections: 80
first_valid_uid: 1001
last_valid_uid: 1001
mail_extra_groups: exim,vmail
mail_location: maildir:%Lh/Maildir
mail_cache_min_mail_count: 1
dotlock_use_excl: yes
fsync_disable: yes
maildir_copy_with_hardlinks: yes
maildir_copy_preserve_filename: yes
mail_drop_priv_before_exec: yes
mail_executable: /bin/imap.sh
mail_plugins: quota imap_quota
auth default:
  mechanisms: PLAIN CRAM-MD5
  default_realm: testing.net
  cache_size: 256
  worker_max_count: 100
  passdb:
    driver: sql
    args: /etc/dovecot-crammd5.conf
  userdb:
    driver: prefetch
plugin:
  quota: maildir