when i did that, i got these messages from openldap.log

Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 fd=14 ACCEPT from IP=127.0.0.1:37821 (IP=0.0.0.0:389)
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=0 BIND dn="cn=vmail,dc=mydomain,dc=com,dc=my" method=128
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=0 BIND dn="cn=vmail,dc=mydomain,dc=com,dc=my" mech=SIMPLE ssf=0
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=0 RESULT tag=97 err=0 text=
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=1 SRCH base="o=domains,dc=mydomain,dc=com,dc=my" scope=2 deref=0 filter="(&(objectClass=mailUser)(accountStatus=active)(enabledService=mail)(enabledService=imapsecured)(|(mail=test03@mydomain.com.my)(&(enabledService=shadowaddress)(shadowAddress=test03@mydomain.com.my))))"
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=1 SEARCH RESULT tag=101 err=0 nentries=1 text=
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=2 BIND anonymous mech=implicit ssf=0
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=2 BIND dn="mail=test03@mydomain.com.my,ou=Users,domainName=mydomain.com.my,o=domains,dc=mydomain,dc=com,dc=my" method=128
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=2 BIND dn="mail=test03@mydomain.com.my,ou=Users,domainName=mydomain.com.my,o=domains,dc=mydomain,dc=com,dc=my" mech=SIMPLE ssf=0
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=2 RESULT tag=97 err=0 text=
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=3 BIND anonymous mech=implicit ssf=0
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=3 BIND dn="cn=vmail,dc=mydomain,dc=com,dc=my" method=128
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=3 BIND dn="cn=vmail,dc=mydomain,dc=com,dc=my" mech=SIMPLE ssf=0
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=3 RESULT tag=97 err=0 text=
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=4 SRCH base="o=domains,dc=mydomain,dc=com,dc=my" scope=2 deref=0 filter="(&(objectClass=mailUser)(accountStatus=active)(enabledService=mail)(enabledService=imapsecured)(|(mail=test03@mydomain.com.my)(&(enabledService=shadowaddress)(shadowAddress=test03@mydomain.com.my))))"
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=4 SRCH attr=storageBaseDirectory mailMessageStore mailQuota
Dec  9 14:45:09 mydomain-mail slapd[10288]: conn=0 op=4 SEARCH RESULT tag=101 err=0 nentries=1 text=

here is my setting for addressbook & global addressbook

$rcmail_config['address_book_type'] = 'sql';

$rcmail_config['ldap_public']["mydomain.com.my"] = array(
    'name'          => 'Global Address Book',
    'hosts'         => array("127.0.0.1"),
    'port'          => 389,
    'use_tls'       => false,
    'user_specific' => true, // If true the base_dn, bind_dn and bind_pass default to the user's IMAP login.
    'base_dn'       => "domainName=%d,o=domains,dc=mydomain,dc=com,dc=my",
    'bind_dn'       => "mail=%u@%d,ou=Users,domainName=%d,o=domains,dc=mydomain,dc=com,dc=my",
    'writable'      => false, // Indicates if we can write to the LDAP directory or not.
    'ldap_version'  => "3",       // using LDAPv3
    'search_fields' => array('mail', 'cn', 'givenName', 'sn'),  // fields to search in
    'name_field'    => 'cn',    // this field represents the contact's name
    'email_field'   => 'mail',  // this field represents the contact's e-mail
    'surname_field' => 'sn',    // this field represents the contact's last name
    'firstname_field' => 'givenName',  // this field represents the contact's first name
    'sort'          => 'cn',    // The field to sort the listing by.
    'scope'         => 'sub',   // search mode: sub|base|list
    'filter'        => "(&(enabledService=mail)(enabledService=deliver)(enabledService=displayedInGlobalAddressBook)(|(objectClass=mailList)(objectClass=mailAlias)(objectClass=mailUser)))", // Search mail users, lists, aliases.
    'fuzzy_search'  => true);   // server allows wildcard search

i checked roundcube's log after enabling it and found this in error log

[09-Dec-2010 16:21:45 +0800]: LDAP Error: No ldap support in this installation of PHP (GET /webmail/?_task=addressbook&_action=list&_source=mydomain.com.my&_remote=1&_=1291882855638&_unlock=1)

so i install php-ldap and that solved it