Article ID: 222060 - View products that this article applies to.
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When you attempt to make a PPTP connection from a Windows NT 4.0 Service Pack 4 (SP4) client to a Windows NT 4.0 SP4 PPTP server running RAS or Routing and Remote Access Service (RRAS), the initial authentication attempt may not work and display an "Error 5: Access Denied" error message. This problem can also occur if your PPTP client and server are running the post-Service Pack 3 PPTP3-fix hotfix.
This problem occurs because there is a timing mismatch during the authentication process between the client and server using MSCHAPv2 authentication.
To resolve this problem, obtain the latest service pack for Microsoft Windows NT 4.0. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/152734/EN-US/ )How to Obtain the Latest Windows NT 4.0 Service Pack
Microsoft has confirmed that this is a problem in Windows NT 4.0. This problem was first corrected in Windows NT 4.0 Service Pack 5.
The hotfix must be applied to the PPTP client computer, installing the hotfix or Windows NT 4.0 Service Pack 5 (SP5) to the PPTP server will not fix this problem. In the very rare case where the client is another RRAS server, there is also a RRAS-specific fix available if you choose to not install SP5.
Article ID: 222060 - Last Review: October 20, 2013 - Revision: 2.2