Running current CVS HEAD I get:
dovecot: Dec 01 13:27:38 Info: Dovecot v1.0-test52 starting up dovecot: Dec 01 13:33:34 Info: imap-login: Login: jtl [69.162.177.245] dovecot: Dec 01 13:41:07 Error: IMAP(jtl): UIDVALIDITY changed (1100294646 -> 110192643 5) in mbox file /var/spool/mail/j/t/jtl dovecot: Dec 01 13:41:07 Error: IMAP(jtl): UIDVALIDITY changed (1100294646 -> 110192643 5) in mbox file /var/spool/mail/j/t/jtl dovecot: Dec 01 13:42:39 Info: imap-login: Login: jtl [69.x.x.x] dovecot: Dec 01 13:42:39 Error: IMAP(jtl): UIDVALIDITY changed (1100294646 -> 110192643 5) in mbox file /var/spool/mail/j/t/jtl dovecot: Dec 01 13:42:39 Error: IMAP(jtl): UIDVALIDITY changed (1100294646 -> 110192643 5) in mbox file /var/spool/mail/j/t/jtl dovecot: Dec 01 13:43:59 Info: imap-login: Login: jtl [69.x.x.x] dovecot: Dec 01 13:43:59 Error: IMAP(jtl): Corrupted index cache file /users/j/t/jtl/.i map/INBOX/dovecot.index.cache: indexid changed dovecot: Dec 01 13:47:24 Error: IMAP(jtl): file mbox-lock.c: line 493 (mbox_lock): asse rtion failed: (lock_type == F_RDLCK || ibox->mbox_lock_type != F_RDLCK) dovecot: Dec 01 13:47:25 Error: child 17528 (imap) killed with signal 6 dovecot: Dec 01 13:47:41 Info: imap-login: Login: jtl [69.x.x.x] dovecot: Dec 01 13:50:49 Error: IMAP(jtl): UIDVALIDITY changed (1101926435 -> 110192703 6) in mbox file /var/spool/mail/j/t/jtl dovecot: Dec 01 13:55:27 Info: imap-login: Login: jtl [69.x.x.x] dovecot: Dec 01 13:55:27 Error: IMAP(jtl): UIDVALIDITY changed (1101926435 -> 110192703 6) in mbox file /var/spool/mail/j/t/jtl dovecot: Dec 01 13:56:15 Info: imap-login: Login: jtl [69.x.x.x] dovecot: Dec 01 13:56:15 Error: IMAP(jtl): UIDVALIDITY changed (1101926435 -> 110192703 6) in mbox file /var/spool/mail/j/t/jtl
Using Thunderbird-0.9. Dovecot is running on RHEL 3, on top of Redhat/Sistina GFS (clustered filesystem.) Currently I'm keeping it on one node to avoid possible GFS locking issues. I'm running with mmap_disabled=yes, mbox format. Most of the 1.0-test builds I have done eventually corrupt their index files, and show strange behavior (click on a message in the folder view, and an entirely different message opens... delete three or four messages and expunge, the messages instantly reappear as unseen.). I typically wipe the .imap directories between different builds of Dovecot.
I've been following the -test code for a couple of months now, just to see how it does, because we're running UW IMAPd and are excited to have a way to increase the performance of our mail cluster (indexes) without having to move away from mbox.
Let me know if there's more information I could provide that would be helpful.
Jim