If Internet Explorer is configured with the Use HTTP 1.1 through proxy connections setting and NTLM authentication is configured on both the Web proxy (such as Microsoft Internet Security and Acceleration Server 2000) and the Web server (such as Microsoft Internet Information Services), Internet Explorer does not authenticate with the Web server and you receive the following error message:

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This issue is caused by incorrect detection of HTTP keep-alives while Wininet.dll processes the NTLM challenge from the Web server.

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A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix has the file attributes (or later) that are listed in the following tables. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

The English version of this fix for Internet Explorer 5.5 Service Pack (SP) 2 should have the following file attributes or later:

   Date         Time   Version        Size     File name
   -------------------------------------------------------
   07-Jun-2002  15:11  5.50.4918.700  481,552  Wininet.dll 
				

The English version of this fix for Internet Explorer 6 should have the following file attributes or later:

   Date         Time   Version        Size     File name
   -------------------------------------------------------
   07-Jun-2002  15:07  6.00.2718.700  583,168  Wininet.dll 
				

The English version of this fix for Internet Explorer 6 SP1 should have the following file attributes or later:

   Date         Time   Version        Size     File name
   -------------------------------------------------------
   23-Oct-2002  14:30  6.0.2800.1130  585,728  Wininet.dll
					

Note that you must correctly configure the HTTP Keep Alive feature to use NTLM authentication.

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To work around this problem, do not use the Use HTTP 1.1 through proxy connections setting. To view or change this setting, click Internet Options on the Tools menu, click the Advanced tab, and then scroll to the HTTP 1.1 settings section.

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Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

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