When you upgrade Windows 2000 Server that is running Microsoft Internet Security and Acceleration (ISA) Server 2000 Service Pack 1 (SP1) to Windows Server 2003, clients computers that are running the Microsoft Firewall Client cannot connect to the Internet.
When you update the ISA server in the Microsoft Firewall Client program, the server is updated, but the client computer cannot connect to the Internet.
This behavior is caused by the W3proxy service hanging when it initializes the listening sockets.
To fix this problem, disable backlog monitoring in Windows Server 2003:
1. Use the Registry Editor to navigate to:
2. Add Value Name DisableBacklogMonitor, a REG_DWORD data type, and set the data value to 1.
3. Exit the Registry Editor.
4. Restart Windows Server 2003.