Article ID: 938305 - View products that this article applies to.
Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/256986/ )Description of the Microsoft Windows registry
You are using Windows Internet Explorer 7. You try to log on to a Web site that requires Kerberos version 5 protocol authentication. However, you are prompted three times for your user credentials, even though you enter the correct information every time that you are prompted to do this. When you try to log on the Web site for the third time, you receive the following error message:
HTTP Error 401.1 - Unauthorized: Access is denied due to invalid credentials. Internet Information Services (IIS)
This problem occurs if the Web site uses a CNAME resource record in the Domain Name System (DNS) to contact the server that initiates Kerberos authentication. When you use Internet Explorer 7 to access the Web site, Internet Explorer 7 uses the host name of the server instead of the CNAME resource record to contact the server. However, only the Service Principal Name (SPN) for the CNAME resource record is registered on the account that the server uses for the authentication. Therefore, the authentication process does not work.
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
To resolve this problem, install the hotfix that is mentioned in the Microsoft Knowledge Base article 911149. Then, enable the 911149 hotfix on the computer. To do this, follow these steps:
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/911149/ )Error message in Internet Explorer when you try to access a Web site that requires Kerberos authentication on a Windows XP-based computer: "HTTP Error 401 - Unauthorized: Access is denied due to invalid credentials"