On a Windows Server 2008-based computer or a Windows Vista Service Pack 1-based computer, all services or processes that require authentication may stop responding.

For example, when you type your user name and password, the system stops responding at the “Welcome” screen.

Consider the following scenario:

• You have a computer that is running Windows Vista or Windows Server 2008.
• You try to log on to a Windows Server 2008-based terminal server by using smart card authentication.

In this scenario, the logon operation fails. Additionally, you receive a “0xC000040C” error message.

Note: The “0xC000040C” error code means that the revocation status of the domain controller certificate that is used for smart card authentication cannot be determined.

This issue occurs when the cached certificate revocation list (CRL) of the domain controller certificate on the client has expired.

When you access a network-attached storage device after you upgrade to Windows Server 2008, to Windows Vista, to Windows Server 2003, or to Windows XP, you may experience authentication issues. Typically, you receive an error message that states that access is denied or that the operating system cannot log on the user. This issue occurs even though you provide the correct user name and the correct password.

On a Windows Vista-based computer, you try to access files on a Web Distributed Authoring and Versioning (WebDAV) site that uses only Digest authentication. However, the process may fail after you are prompted three times for your user credentials and password.

If you use a network trace when this problem occurs, the network trace may indicate that the WebDAV server generates a code 401 (Authorization Required) error.

Consider the following scenario:

• Your computer is in a wireless network environment that uses Extensible Authentication Protocol-Transport Layer Security (EAP-TLS).
• You use SmartCard-only authentication for the wireless connection authentication.

In this scenario, when you log on to a Windows Vista-based client computer, you may receive the following error message in the toolbar:

Cannot connect to SSID: Please contact network administrator.

Note: In this message, the SSID placeholder represents the wireless network connection.

Therefore, you cannot connect to the wireless network. In this case, you must manually reconnect to the wireless network.

This problem does not occur when you log on to the computer for the first time. When you log on for the first time, you receive the following message:

Wireless Network Connection:

Please click here to select the certificate for the following network connection or other qualification information.

After you provide the correct information, you can successfully connect to the wireless network.

Note: This problem does not occur in Windows XP. In Windows XP, you are prompted to provide the related smart card information. Then, you can successfully connect to the wireless network.

Windows activation in Windows Server 2008 or in Windows Vista fails when you configure a non-Microsoft firewall to use HTTPS authentication to enable access to the Internet.

Consider the following scenario.

• You are running a Windows Vista-based computer.
• You use a wireless access point that is configured to use Wireless Encryption Protocol (WEP) and shared-mode network authentication.
• In the properties of the wireless network connection, you click View Wireless Networks, and then you click Choose a wireless network.

When you double-click the WEP-shared mode access point in this scenario, you cannot connect to the access point. Instead, you receive the following error message:

Windows cannot connect to access_point.

On a Windows Vista-based client computer, you access an online document that is on a site that uses Windows Live ID (WLID) authentication. Then, you are prompted for user credentials two times. However, you expect to be prompted for user credentials only one time.

You are connected to a remote network over a virtual private network (VPN) connection from Windows Vista. However, every time that you try to access a local resource on another computer, you are prompted for authentication. You expect that stored credentials for the resource that you are trying to access will be used for local access.

On a computer that is running Windows Vista, you try to establish a dial-up virtual private network (VPN) connection that uses Extensible Authentication Protocol-Transport Layer Security (EAP-TLS) for authentication.

If there are no user certificates on the computer, you may receive the following error message:

Error: 0×80420100: There was an unknown error.