@dsefcik:
Can you describe what it does? You seem to think we should not need to add this.
http://www.squid-cache.org/Versions/v3/3.1/manuals/squid_ldap_auth.html
-R do not follow referrals
Read this: LDAP Referrals, mainly:
An LDAP referral is a domain controller's way of indicating to a client application that it does not have a copy of a requested object (or, more precisely, that it does not hold the section of the directory tree where that object would be, if in fact it exists) and giving the client a location that is more likely to hold the object, which the client uses as the basis for a DNS search for a domain controller.
Either you are querying wrong DCs or there's something wrong with your setup really.