dovecot - Dec 2010 - panic with lmtp proxy (assertion failed)

Hello!

Got a panic&assertion failed with LMTP proxy. Target Dovecot LMTP  
server hanged and Dovecot LMTP proxy server started logging  
panics/assertions. Core dumps were disabled unfortunately, so I don't  
know if this is helpful at all:

Dec 29 15:41:58 lmtp(8853): Panic: file lmtp-proxy.c: line 370  
(lmtp_proxy_output_timeout): assertion failed: (proxy->data_input->eof)
Dec 29 15:41:58 lmtp(8853): Error: Raw backtrace:  
/usr/local/dovecot20/lib/dovecot/libdovecot.so.0 [0xb76aa7c1] ->  
/usr/local/dovecot20/lib/dovecot/libdovecot.so.0 [0xb76aa83f] ->  
/usr/local/dovecot20/lib/dovecot/libdovecot.so.0(i_error+0)  
[0xb76aab14] -> dovecot/lmtp [0x804e3f4] ->  
/usr/local/dovecot20/lib/dovecot/libdovecot.so.0(io_loop_handle_timeouts+0xe0)  
[0xb76b7720] ->  
/usr/local/dovecot20/lib/dovecot/libdovecot.so.0(io_loop_handler_run+0x8b)  
[0xb76b843b] ->  
/usr/local/dovecot20/lib/dovecot/libdovecot.so.0(io_loop_run+0x40)  
[0xb76b7340] ->  
/usr/local/dovecot20/lib/dovecot/libdovecot.so.0(master_service_run+0x2a)  
[0xb76a31fa] -> dovecot/lmtp(main+0x170) [0x804b380] ->  
/lib/i686/cmov/libc.so.6(__libc_start_main+0xe5) [0xb7516455] ->  
dovecot/lmtp [0x804b171]
Dec 29 15:41:58 master: Error: service(lmtp): child 8853 killed with  
signal 6 (core dumps disabled)

doveconf -n output:
$ /usr/local/dovecot20/bin/doveconf -c  
/usr/local/dovecot20/etc/dovecot/dovecot-lmtpproxy.conf -n
# 2.0.8: /usr/local/dovecot20/etc/dovecot/dovecot-lmtpproxy.conf
# OS: Linux 2.6.31.5 i686 Debian 5.0.7
auth_cache_negative_ttl = 0
auth_mechanisms = plain login
auth_socket_path = /usr/local/dovecot20/var/run/dovecot-lmtpproxy/auth-userdb
auth_username_chars =  
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@&:
auth_verbose = yes
base_dir = /usr/local/dovecot20/var/run/dovecot-lmtpproxy/
disable_plaintext_auth = no
listen = *
lmtp_proxy = yes
log_path = /var/log/dovecot.lmtpproxy/dovecot.lmtpproxy.log
login_log_format_elements = user=<%u> service=%s method=%m rip=%r lip=%l
%c
login_trusted_networks = 172.16.83.64/26
mail_fsync = never
mail_gid = 1000
mail_location = maildir:~/Maildir
mail_uid = 1000
maildir_very_dirty_syncs = yes
passdb {
   args = /usr/local/dovecot20/etc/dovecot/dovecot-sql.lmtpproxy.alias.conf
   driver = sql
}
postmaster_address = postmaster at example.com
protocols = lmtp
service auth-worker {
   user = $default_internal_user
}
service auth {
   client_limit = 8192
   unix_listener auth-userdb {
     mode = 0666
   }
}
service imap-login {
   process_min_avail = 1
   service_count = 0
   vsz_limit = 1 G
}
service imap {
   process_limit = 2048
}
service lmtp {
   inet_listener lmtp {
     address = *
     port = 24
   }
   process_min_avail = 1
   service_count = 0
   user = mailuser
   vsz_limit = 512 M
}
service pop3-login {
   process_min_avail = 1
   service_count = 0
   vsz_limit = 1 G
}
service pop3 {
   process_limit = 2048
}
ssl = no
verbose_proctitle = yes
protocol lda {
   info_log_path    log_path    mail_fsync = optimized
}
protocol imap {
   imap_client_workarounds = delay-newmail
   mail_max_userip_connections = 20
}
protocol lmtp {
   mail_fsync = optimized
}
protocol pop3 {
   mail_max_userip_connections = 5
   pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
}