What is Error 1937?
Windows System Error Code 1937, known as ERROR_NTLM_BLOCKED, is a RPC & Network error that occurs during Remote Procedure Call (RPC) and network communication. The error indicates that: Authentication failed because NTLM authentication has been disabled. When this error is encountered, the Windows operating system was unable to complete the requested operation within the network services subsystem. The error code 1937 is returned by the GetLastError() function and provides developers with a specific identifier to diagnose the root cause of the failure. The symbolic name ERROR_NTLM_BLOCKED maps directly to this numeric code and is commonly referenced in Microsoft documentation, developer forums, and system logs. Understanding this error and its context within Remote Procedure Call (RPC) and network communication is essential for effective troubleshooting.
Common Causes
- System resource conflict: Authentication failed because NTLM authentication has been disabled.
- RPC server is unavailable
- Network connectivity issues
- Firewall blocking required ports
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Read the full guide →Step-by-Step Solutions
- Open Command Prompt as Administrator
- Run: netsh winsock reset
- Run: netsh int ip reset
- Run: ipconfig /flushdns
- Restart your computer
Video Tutorials
Diagnostic Command
Run this PowerShell command to find related events in your system log:
Get-EventLog -LogName System -Newest 20 | Where-Object {$_.Message -like "*1937*" -or $_.Message -like "*ERROR_NTLM_BLOCKED*"} | Format-List💡 Open PowerShell as Administrator, paste the command above, and press Enter.
Prevention Tips
- Monitor network health regularly
- Document firewall rules
- Test connectivity after infrastructure changes