Run these command before you can do ldap search from third party clients:
/opt/zimbra/libexec/zmldapanon -e /opt/zimbra/libexec/zmldapanon -d
That enable anonymous bind and disable it again. Strange. But that is required for version:
Release 7.1.3_GA_3346.RHEL6_64_20110928134428 CentOS6_64 FOSS edition.
May be a bug.