Improperly configured registry keys (UpperFilters/LowerFilters) can prevent the USB bus from loading. Solutions to Fix Mastercam Error 39 Follow these steps in order to resolve the issue. Method 1: Disable Memory Integrity (Core Isolation) This is the most common fix for Error 39 in Windows 10/11. Open the Start Menu and type Windows Security . Go to Device Security . Click on Core isolation details . Toggle Memory integrity to Off . Restart your computer . Method 2: Clean Registry Upper/Lower Filters
"Virtual USB Bus Error 39: The driver returned a failed result for a request to retrieve the device descriptor."
Windows generates when it cannot load a hardware driver. For Mastercam users, this error specifically targets the virtual USB emulator or the Sentinel HASP dongle driver. The most common causes include:
If you can tell me and if you are using a physical or virtual HASP , I can give you a more specific fix. Share public link
Since this is a "Virtual USB Bus" error, reinstalling the Sentinel HASP/LDK License Manager drivers is a common troubleshooting step for HASP-related errors Check for Multiple Instances: Mastercam X7-2022 Virtual Usb Bus Error 39
Fixing Mastercam Virtual USB Bus Error 39: Complete Troubleshooting Guide
I can provide the precise folder paths and command lines for your exact situation. Share public link
Once Windows boots up, lock this setting so it survives future restarts:
Modern versions of Windows 10 and 11 include a security feature called Core Isolation Open the Start Menu and type Windows Security
The "Mastercam Virtual USB Bus Error 39" is a classic case of Windows security evolution outpacing legacy industrial software. While the error message looks catastrophic, it is merely a driver handshake failure—not a dead license or broken hardware.
Error 39 is a Windows device manager code indicating that the driver for the device is either:
If Error 39 started after a Windows update:
If the virtual USB bus registry keys become corrupted, Windows fails to initialize the driver stack. Press Windows Key + R , type regedit , and hit . Toggle Memory integrity to Off
Navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\36FC9E60-C465-11CF-8056-444553540000 .
This error is especially common in Mastercam versions because these versions use a specific generation of SafeNet/Aladdin HASP drivers. Recent Windows updates (particularly Windows 10/11) often deprecate or block older, unsigned, or insecure drivers.
To resolve Error 39 in Mastercam X7-2022, follow these step-by-step troubleshooting steps:
