Hello Timo,
I'm testing the latest hg version from the 1.2 series and get the following in dovecot's error log as soon as I try to access the virtual mailbox
Dec 11 18:23:07 ubuntu-test dovecot: IMAP(xxxxx): virtual index /etc/dovecot/virtual/unseen: Broken mailbox list
$ cat dovecot-virtual * unseen
$ dovecot -n
# 1.2.8: /etc/dovecot/dovecot.conf # OS: Linux 2.6.31-16-generic-pae i686 Ubuntu 9.10 protocols: imap imaps managesieve 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(managesieve): /usr/lib/dovecot/managesieve-login verbose_proctitle: yes mail_location: maildir:~/.maildir mail_debug: yes mail_drop_priv_before_exec: yes mail_executable(default): /usr/lib/dovecot/rawlog /usr/lib/dovecot/wrapper.sh mail_executable(imap): /usr/lib/dovecot/rawlog /usr/lib/dovecot/wrapper.sh mail_executable(managesieve): /usr/lib/dovecot/managesieve mail_plugins(default): expire fts fts_squat virtual quota imap_quota mail_log acl mail_plugins(imap): expire fts fts_squat virtual quota imap_quota mail_log acl mail_plugins(managesieve): mail_plugin_dir(default): /usr/lib/dovecot/modules/imap mail_plugin_dir(imap): /usr/lib/dovecot/modules/imap mail_plugin_dir(managesieve): /usr/lib/dovecot/modules/managesieve mail_log_max_lines_per_sec: 0 namespace: type: private separator: / inbox: yes list: yes subscriptions: yes namespace: type: private separator: / prefix: virtual/ location: virtual:/etc/dovecot/virtual:INDEX=~/.maildir/control:CONTROL=~/.maildir/control list: children lda: postmaster_address: postmaster@ubuntu hostname: ubuntu mail_plugins: sieve virtual expire quota acl mail_plugin_dir: /usr/lib/dovecot/modules/lda deliver_log_format: msgid=%m: from=%f: %$ log_path: /var/log/deliver.log info_log_path: /var/log/deliver.log sendmail_path: /usr/lib/sendmail rejection_subject: Rejected: %s rejection_reason: Your message to <%t> was automatically rejected:%n%r auth_socket_path: /var/run/dovecot/auth-master auth default: passdb: driver: sql args: /etc/dovecot/dovecot-sql.conf userdb: driver: sql args: /etc/dovecot/dovecot-sql.conf socket: type: listen client: path: /var/spool/postfix/private/auth mode: 432 user: postfix group: postfix master: path: /var/run/dovecot/auth-master mode: 438 plugin: quota: dict:user::proxy::dictionary expire: Trash 1 "INBOX/log check" 1 expire_dict: proxy::dictionary mail_log_events: delete undelete expunge copy mailbox_delete mailbox_rename flag_change mail_log_fields: uid box msgid size flags sieve: ~/.dovecot.sieve sieve_dir: ~/sieve deliver_log_format: msgid=%m: from=%f: %$ fts: squat fts_squat: partial=4 full=10 dict: dictionary: mysql:/etc/dovecot/dovecot-dict-sql.conf