After putting ldap.jar and jndi.jar into /var/mqsi/shared-classes and restarting the broker, I see the error in the log:
Mar 12 10:53:07 swim05 WebSphere Broker v6002[8207]: (S05ADSBBKR.S05ADSBEG)[-1 ...
well, that LDAP object S05NPBRK.36b18d29-1101-0000-0080-900bdfece5f3 is not set or created by us, i think it is used internally by WMB. From the LDAP app you cannot see it.