I solve the problem on Win7 (temporary) I set RC4-HMAC type for kerberos transactions in Local Security Policy http://technet.microsoft.com/en-us/library/dd560670%28WS.10%29.aspx Now both keys on client machine are in RC4-HMAC type (krbtgt and HTTP/fqdn_of_proxy) That's help in my case. Sounds not so good if this be AES256, but i think it's before of mixed mode of AD (2003 and 2008). Try to communicate with microsoft about this. P.S. Sorry for my english :) Regards, Dmitry -- View this message in context: http://squid-web-proxy-cache.1019090.n4.nabble.com/Authentication-using-squid-kerb-auth-with-Internet-Explorer-8-on-Windows-Server-2008-R2-tp3013070p3019158.html Sent from the Squid - Users mailing list archive at Nabble.com.