dovecot - Nov 2009 - Panic: Message unexpectedly expunged from index

Hello,

I just installed Fedora 11 with Dovecot 1.2.6 and am now seeing a steady
stream of these in maillog:

Nov 15 15:52:03 sendmail dovecot: POP3(<username>): Panic: Message
unexpectedly expunged from index
Nov 15 15:52:03 sendmail dovecot: POP3(<username>): Raw backtrace: pop3
[0x4930ab] -> pop3 [0x493123] -> pop3 [0x4927b6] -> pop3 [0x43ddd4]
-> pop3
[0x43de84] -> pop3(index_mail_set_seq+0x146) [0x449c16] -> pop3
[0x43e129] -> pop3(index_storage_search_next_nonblock+0x141) [0x44d5c1] ->
pop3(mailbox_search_next_nonblock+0x20) [0x45b580] ->
pop3(mailbox_search_next+0x26) [0x45b5d6] -> pop3 [0x419ef9] ->
pop3(client_command_execute+0x666) [0x41abd6] ->
pop3(client_handle_input+0x80) [0x418f80] -> pop3(io_loop_handler_run+0xbd)
[0x49b02d] -> pop3(io_loop_run+0x18) [0x49a498] -> pop3(main+0x526)
[0x41b286] -> /lib64/libc.so.6(__libc_start_main+0xfd) [0x3a9b61ea2d] ->
pop3 [0x418809]
Nov 15 15:52:03 sendmail dovecot: dovecot: child 26792 (pop3) killed with
signal 6 (core dumps disabled)

I see nothing about this in the mail archives or on the internet!
What could be happening and how do I fix?
I'm also seeing lots of these:

Nov 15 11:26:24 sendmail dovecot: POP3(<username>): Log synchronization
error at seq=12646,offset=172 for /var/spool/mail/.imap/INBOX/dovecot.index:
Extension introduction for unknown id 1
Nov 15 11:26:24 sendmail dovecot: POP3(<username>): fscking index file
/var/spool/mail/.imap/INBOX/dovecot.index

Here are the only things I messed with in dovecot.conf:

protocols = pop3
mail_location = mbox:/var/spool/mail:INBOX=/var/spool/mail/%u
mbox_very_dirty_syncs = yes

Thanks in advance,

Cliff