[Dovecot] SIGSEGV login process

[Maxim]

Hi all.
I recently upgraded from 1.0.0 to 1.0.7 version and found that process 
imap-login begins randomly crash:

pid 29997 (imap-login), uid 143: exited on signal 11 (core dumped)
pid 32189 (imap-login), uid 143: exited on signal 11 (core dumped)
pid 32121 (imap-login), uid 143: exited on signal 11 (core dumped)
pid 31309 (imap-login), uid 143: exited on signal 11 (core dumped)

i guess that it happens during high load on CPU (but just guess)
no anything upon upgrade changed - traffic, config are the same. can anyone 
help me?
running FreeBSD 6.2, compiled from port with mysql, lda, kqueue, pop3 support.

mail# dovecot -n
# 1.0.7: /usr/local/etc/dovecot.conf
protocols: imap pop3 pop3s imaps
listen(default): *:143
listen(imap): *:143
listen(pop3): *:110
ssl_listen(default): *:993
ssl_listen(imap): *:993
ssl_listen(pop3): *:995
ssl_cert_file: /usr/local/etc/ssl_mail/dovecot.pem
ssl_key_file: /usr/local/etc/ssl_mail/dovecot.pem
ssl_cipher_list: ALL:!LOW
disable_plaintext_auth: no
login_dir: /var/run/dovecot/login
login_executable(default): /usr/local/libexec/dovecot/imap-login
login_executable(imap): /usr/local/libexec/dovecot/imap-login
login_executable(pop3): /usr/local/libexec/dovecot/pop3-login
verbose_proctitle: yes
first_valid_uid: 26
last_valid_uid: 26
mail_extra_groups: mail
mail_location: maildir:~/Maildir
mmap_disable: yes
mail_executable(default): /usr/local/libexec/dovecot/imap
mail_executable(imap): /usr/local/libexec/dovecot/imap
mail_executable(pop3): /usr/local/libexec/dovecot/pop3
mail_plugins(default): quota imap_quota
mail_plugins(imap): quota imap_quota
mail_plugins(pop3): quota
mail_plugin_dir(default): /usr/local/lib/dovecot/imap
mail_plugin_dir(imap): /usr/local/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/local/lib/dovecot/pop3
imap_client_workarounds(default): delay-newmail outlook-idle netscape-eoh 
tb-extra-mailbox-sep
imap_client_workarounds(imap): delay-newmail outlook-idle netscape-eoh 
tb-extra-mailbox-sep
imap_client_workarounds(pop3): outlook-idle
pop3_uidl_format(default):
pop3_uidl_format(imap):
pop3_uidl_format(pop3): %08Xu%08Xv
pop3_client_workarounds(default):
pop3_client_workarounds(imap):
pop3_client_workarounds(pop3): outlook-no-nuls oe-ns-eoh
auth default:
  mechanisms: plain cram-md5 digest-md5 apop login
  default_realm: proc.ru
  passdb:
    driver: sql
    args: /usr/local/etc/dovecot-sql.conf
  userdb:
    driver: sql
    args: /usr/local/etc/dovecot-sql.conf 

mail# grep -v '^ *\(#.*\)\?$' /usr/local/etc/dovecot-sql.conf
driver = mysql
connect = host=/tmp/mysql.sock dbname=exim_users user=exim password=**
default_pass_scheme = PLAIN
password_query = SELECT concat(pw_name, '@', domain) as user, pw_clear_passwd 
as password FROM vusers WHERE pw_name = '%n' AND domain = '%d'
user_query = SELECT pw_dir AS home, 26 AS uid, 26 AS gid, 
concat('maildir:storage=', quota*1024) AS quota FROM vusers WHERE pw_name 
= '%n' AND domain = '%d'

backtrace from core file:

mail# 
gdb ./work/dovecot-1.0.7/src/imap-login/imap-login /var/run/dovecot/login/tmp/imap-login.core
GNU gdb 6.1.1 [FreeBSD]
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386-marcel-freebsd"...(no debugging symbols 
found)...

warning: exec file is newer than core file.
Core was generated by `imap-login'.
Program terminated with signal 11, Segmentation fault.
Reading symbols from /usr/lib/libssl.so.4...(no debugging symbols 
found)...done.
Loaded symbols for /usr/lib/libssl.so.4
Reading symbols from /lib/libcrypto.so.4...(no debugging symbols 
found)...done.
Loaded symbols for /lib/libcrypto.so.4
Reading symbols from /lib/libc.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /libexec/ld-elf.so.1...(no debugging symbols 
found)...done.
Loaded symbols for /libexec/ld-elf.so.1
#0  0x08051e2d in auth_client_request_continue ()
(gdb) bt
#0  0x08051e2d in auth_client_request_continue ()
#1  0x0804b8db in client_auth_input ()
#2  0x080562ec in io_loop_handler_run ()
#3  0x0805599d in io_loop_run ()
#4  0x0804d963 in main ()
(gdb)       


or what anything info should i provide?