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Microsoft KB Archive/124648

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Knowledge Base

DC21040 Causes Windows NT 3.5 to Stop Responding (Hang)

Article ID: 124648

Article Last Modified on 11/1/2006


  • Microsoft Windows NT Workstation 3.5
  • Microsoft Windows NT Server 3.5

This article was previously published under Q124648


Network connections on your Windows NT computer are lost, new users cannot connect, and applications requiring network access stop responding (hang). Applications running locally may continue to function, but may also eventually hang.


You are using the DC21040.SYS Ethernet driver. A problem with the driver causes the protocol to run out of resources when dealing with loopback packets. The system becomes unable to accept anymore incoming packets from the adapter. Loopback occurs when an application is accessing a local resource (for example, a UNC file name) rather than a local driver letter.


Microsoft has confirmed this to be a problem in Windows NT Workstation and Windows NT Server version 3.5. This problem has been corrected in the latest U.S. Service Pack for Windows NT version 3.5. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K

The third-party products discussed here are manufactured by vendors independent of Microsoft; we make no warranty, implied or otherwise, regarding these products' performance or reliability.

Additional query words: prodnt DEC 2100 cpu

Keywords: KB124648