Kerberos authentication ticket - Event ID 4768 - Audit failure

I am using kerberos to authenticate a user and its failing. Audit failure details in event viewer are following

A Kerberos authentication ticket (TGT) was requested.

Account Information:
Account Name:
 HTTP
Supplied Realm Name:
TEST.COM
User ID:
 NULL SID 

Service Information:
Service Name:
 krbtgt/TEST.COM
Service ID:
 NULL SID

Network Information:
Client Address:
::ffff:2.2.2.60
Client Port:
 42062

Additional Information:
Ticket Options:
0x40800000
Result Code:
 0x6
Ticket Encryption Type:
0xffffffff
Pre-Authentication Type:
-

Certificate Information:
Certificate Issuer Name:

Certificate Serial Number:

Certificate Thumbprint:


Certificate information is only provided if a certificate was used for pre-authentication.
Pre-authentication types, ticket options, encryption types and result codes are defined in RFC 4120.

The result code 0x6 means that user doesn't exist in Kerberos database but i have a user already configured in AD. This is windows server 2008 (non-R2) and user account name is "axax" and User logon name is "HTTP/axax.test.com". The domain name is test.com. From wireshark, i can see that my client is sending AS-REQ which has correct 2 name string items HTTP & axax.test.com. I am not sure why is it failing.

I found the problem. There is software bug on Microsoft 2008 (non R2). Issue resolved after installing the hotfix (KB951191).