Problems accessing Zimbra Ldap

[wintermute]

Hello!
I have successfully installed Zimbra on 2 Servers: 1 for ldap, 1 for the rest.
Zimbra is working.
Now I'd like to access the Ldap Server (read only) via external software.

What works:
- telnet ldap.mydomain.com 389
- Connecting to ldap.mydomain.com using external LDAP Browsers like Softerra LDAP Browser

What does not work:
Accessing ldap data. In Zimbra Log I allways get messages like this:
Sep 26 10:13:23 ldap slapd[16021]: conn=1093 op=28 do_search: get_ctrls failed

Can you help me out of this?
Thanks in advance

[wintermute]

Problem sovled.
I tried to check out the RootDN. It works checking out dc=com.