Replication - ERROR: Constraint violation

[Marek Pasovsky <openldap@qls.cz>]

Hello,
I'm trying to setup replication between two ldap servers (openldap 2.0.27).
Both servers are running fine, just the changes to the records on the master
do not propagate to the slave (IMHO updatedn on slave is set correctly).
When I make changes to the master, they are written to slurpd.replog but 
then
end in replicaname:389.rej file with error message:
ERROR: Constraint violation

Do you have any idea what I have done wrong?? Both of my slapd.conf 
files are
below.

Thanks for any hints

Marek

slapd.conf on slave:

include         /etc/openldap/schema/core.schema
include         /etc/openldap/schema/openldap.schema
updatedn "cn=admin,dc=qls,dc=cz"
pidfile         //var/run/slapd.pid
argsfile        //var/run/slapd.args
access to attr=clearPassword
        by dn="cn=admin,dc=qls,dc=cz" write
        by self write
        by anonymous auth
        by * search
access to attr=userPassword
        by dn="cn=admin,dc=qls,dc=cz" write
        by self write
        by anonymous auth
        by * search
access to *
        by dn="cn=admin,dc=qls,dc=cz" write
        by self write
        by * read
database        ldbm
suffix          "dc=qls,dc=cz"
rootdn          "cn=admin,dc=qls,dc=cz"
rootpw          secret
directory       /var/lib/ldap
index   objectClass,uid,uidNumber,gidNumber             eq
index   cn,mail,surname,givenname                       eq,subinitial

slapd.conf on master:

include         /etc/openldap/schema/core.schema
include         /etc/openldap/schema/openldap.schema
pidfile		//var/run/slapd.pid
argsfile        //var/run/slapd.args
replogfile      /var/lib/ldap/master-slapd.replog
access to attr=clearPassword
        by dn="cn=admin,dc=qls,dc=cz" write
        by self write
        by anonymous auth
        by * search
access to attr=userPassword
        by dn="cn=admin,dc=qls,dc=cz" write
        by self write
        by anonymous auth
        by * search
access to *
        by dn="cn=admin,dc=qls,dc=cz" write
        by self write
        by * read
database        ldbm
suffix          "dc=qls,dc=cz"
rootdn          secret
rootpw          {CRYPT}teRuXbowDj0zY
directory       /var/lib/ldap
index   objectClass,uid,uidNumber,gidNumber             eq
index   cn,mail,surname,givenname                       eq,subinitial
replica host=10.12.4.10:389
      binddn="cn=admin,dc=qls,dc=cz"
      bindmethod=simple credentials=secret