plesk_saslauthd error

[SiharM]

Hi,
I got problem on postfix mail server, my clien sometime can not send mail wuth authentication.
there is error on mail log
May 2 15:34:00 webhost01 plesk_saslauthd[10713]: privileges set to (89:89) (effective 89:89)
May 2 15:34:00 webhost01 plesk_saslauthd[10713]: server fatal error: listen: Socket operation on non-socket
May 2 15:34:00 webhost01 postfix/master[31820]: warning: process /usr/libexec/postfix/plesk_saslauthd pid 10713 exit status 1
May 2 15:34:00 webhost01 postfix/master[31820]: warning: /usr/libexec/postfix/plesk_saslauthd: bad command startup -- throttling


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some part config on master.cf

plesk_virtual unix - n n - - pipe flags=DORhu user=popuseropuser argv=/usr/lib64/plesk-9.0/postfix-local -f ${sender} -d ${recipient} -p /home/qmail/mailnames
mailman unix - n n - - pipe flags=R user=mailman:mailman argv=/usr/lib64/plesk-9.0/postfix-mailman ${nexthop} ${user} ${recipient}
plesk_saslauthd unix y y n - 1 plesk_saslauthd status=5 listen=8 dbpath=/var/spool/postfix/plesk/passwd.db
submission inet n - n - - smtpd
-o smtpd_tls_security_level=may
-o smtpd_sasl_auth_enable=yes
-o smtpd_client_restrictions=permit_sasl_authenticated,reject
-o milter_macro_daemon_name=ORIGINATING

smtp inet n - n - - smtpd
smtps inet n - n - - smtpd
-o smtpd_tls_wrappermode=yes
-o smtpd_sasl_auth_enable=yes
-o smtpd_client_restrictions=permit_sasl_authenticated,reject
-o milter_macro_daemon_name=ORIGINATING

Please help.