SORRY!!! I did this and the error went away:
WPMU Admin Options > Allow New Registrations : Disabled.
WPMU Admin LDAP Options > Disable Public Signup : NO
What happens now is when a user clicks on the signup button it takes them to the WPMU login page. They login and it uses LDAP. There is no local user account signups as everything appears to be going through the LDAP plugin to authenticate.