You may receive an "HTTP 401 Unauthorized" error message when you use SOAP over HTTP and Visual C# .NET XML Web services on a computer that is running Windows XP or Windows Server 2003

When you use SOAP over HTTP and Visual C# .NET XML Web services on a computer that is running Microsoft Windows XP or Microsoft Windows Server 2003, you may intermittently receive an error message that is similar to the following:

System.Net.WebException: The request failed with HTTP status 401: Unauthorized.

This problem occurs when a Web service uses Integrated Windows authentication, and the client passes the appropriate credentials correctly.

Additionally, this problem may occur more frequently when multiple threads on the client try to connect to the network at the same time.
This issue occurs if a request time-out or an abort is not correctly handled.

Software update information

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Microsoft .NET 1.1 Framework service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone 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.


To apply this update, you must have the Microsoft .NET Framework 1.1 Service Pack 1.

Restart requirement

You do not have to restart your computer after you apply this software update.

Software update replacement information

This software update does not replace any other updates.

File information

The English version of this software update has the file attributes (or later file attributes) that are listed in the following table. 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.
For the Microsoft .NET Framework 1.1 Redistributable
   Date         Time   Version        Size       File name   --------------------------------------------------------   07-Oct-2004  07:46  1.1.4322.2038  1,228,800  System.dll
For the Microsoft .NET Framework 1.1 for Windows 2003
   Date         Time   Version        Size       File name   --------------------------------------------------------   14-Oct-2004  02:44  1.1.4322.2038  1,228,800  System.dll
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates

Article ID: 885274 - Last Review: 12/03/2007 18:53:56 - Revision: 3.2

  • Microsoft .NET Framework 1.1 Service Pack 1
  • kbqfe kbhotfixserver kbnetframe110presp2fix kbbug kbfix KB885274