A common cause of this error is that a user makes a typing mistake when performing an operation. Another common cause is when the LDAP client attempts to bind with a DN that does not exist. This often occurs when the user specifies what he or she mistakenly thinks is the administrator DN. For example, the user can specify QSECOFR or Administrator, when the actual administrator DN might be something like cn=Administrator.
For details about the error, look at the QDIRSRV job log as described in Monitor errors and access with the Directory Server job log.