The "Error 39" associated with the Mastercam Virtual USB Bus is a common headache for users running legacy versions of Mastercam on modern Windows operating systems. This error essentially means Windows cannot load the device driver because it may be corrupted, missing, or—most likely—digitally unsigned. The Root Cause: Driver Enforcement
The Virtual USB Bus is a software emulator used to bypass or manage physical Hasp/HL dongle requirements. Windows 10 and 11 require all drivers to have a verified digital signature. Since many virtual USB drivers for Mastercam X7 through 2022 are third-party "cracks" or unsigned emulators, Windows blocks them by default, resulting in the Code 39 status in Device Manager. How to Fix Error 39
💡 The most effective fix is disabling Driver Signature Enforcement. Step 1: Advanced Startup Go to Settings > Update & Security > Recovery. Under Advanced Startup, click Restart Now. Step 2: Startup Settings
Choose Troubleshoot > Advanced Options > Startup Settings > Restart. Step 3: Disable Enforcement
When the list appears, press F7 (Disable driver signature enforcement). Step 4: Reinstall the Driver Open Device Manager.
Find the "Virtual USB Bus" with the yellow exclamation mark. Right-click, select Uninstall device.
Re-run your driver installation script (usually install.bat or similar). Registry and File Integrity
If the driver is signed but still shows Error 39, the registry entry may be corrupted.
Check for UpperFilters/LowerFilters: Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class.
Locate the USB Class GUID: Identify the string matching USB controllers.
Delete Corrupt Values: If UpperFilters or LowerFilters exist and are blank or contain invalid data, delete them and reboot. Long-term Stability
Using a virtual bus is often a workaround for missing hardware or license management issues. For professional environments, the most stable solution is:
Updating to the latest Sentinel HASP/LDK drivers from the official Thales website.
Moving toward Mastercam’s Software Licensing (standard in newer versions), which eliminates the need for a USB bus driver entirely. To help you get back to programming, let me know: Are you using a physical dongle or a software emulator? Which Windows version (10 or 11) are you currently on? Did this error appear after a Windows Update?
I can provide specific command-line steps if the manual reinstall fails.
Troubleshooting Mastercam Virtual USB Bus Error 39 (Updated for 2022-2025)
Encountering "Error Code 39" with the Mastercam Virtual USB Bus typically indicates that Windows cannot load the device driver because it is either corrupted or incompatible with modern security features. This issue frequently affects older versions like Mastercam X7 when run on updated versions of Windows 10 and Windows 11.
The following guide outlines the most effective solutions found by technicians and users to resolve this driver conflict. 1. Disable Core Isolation (Memory Integrity) mastercam x72022 virtual usb bus error 39 updated
The most common cause for Error 39 in recent Windows updates is a security feature called Core Isolation. This feature often blocks older virtual drivers from loading. Open the Start menu and search for Windows Security. Navigate to Device security in the left-hand panel. Select Core isolation details. Toggle the Memory integrity switch to Off. Restart your computer to apply the changes. 2. Modify Windows Registry (Delete Filters)
If disabling Core Isolation does not work, corrupted "UpperFilters" or "LowerFilters" in the Windows Registry may be preventing the driver from loading. Press Windows + R, type regedit, and press Enter.
Navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\. Search for the class key associated with your USB device.
In the right-hand pane, locate and Delete any entries named UpperFilters or LowerFilters. Restart your PC. 3. Update the Sentinel HASP Driver
Mastercam relies on Sentinel HASP/LDK drivers for licensing. Error 39 can occur if the installed driver version is too old for your operating system. How to Fix USB Error Code 39 In Windows 10/8/7 [Tutorial]
The "Virtual USB Bus Error 39" in Mastercam (X7 through 2022) typically occurs when Windows cannot load the driver because it’s corrupted, missing, or blocked by security features like Core Isolation. The Story of the Ghost in the USB
Marcus stared at his screen, where a deadline for a critical milling job loomed. He’d just upgraded his workstation to Windows 11, but instead of the sleek performance he expected, Mastercam X7-2022 refused to launch. In the Device Manager, a yellow exclamation mark mocked him next to the Virtual USB MultiKey.
"The driver may be corrupted or missing. (Code 39)," the error read.
He tried the usual dance: unplugging the HASP dongle and moving it to a different port, but the error remained. He dug into the Mastercam user forums and found his first clue: Core Isolation.
The First Fix: Breaking the ShieldMarcus opened Windows Security, navigated to Device Security, and clicked on Core Isolation details. He flipped the Memory Integrity switch to Off and restarted his PC.
Upon reboot, the yellow exclamation mark was gone, but Mastercam still wouldn't budge. He realized his Windows User profile might have become corrupted after a previous crash while running multiple instances of the software.
The Final Fix: The Registry CleansingDetermined, Marcus opened Regedit. He navigated deep into the system's class settings:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\36FC9E60-C465-11CF-8098-00AA004C324E.
On the right, he found the culprits: UpperFilters and LowerFilters. He deleted them, closed the registry, and performed one final reboot. This time, as the desktop loaded, the HASP light flickered to life. Mastercam launched smoothly, and the "ghost" in the USB bus was finally laid to rest.
Fixing Mastercam Virtual USB Bus Error Code 39 (X7–2022) Encountering the Virtual USB Bus Error Code 39 while trying to launch Mastercam (versions X7 through 2022) is a common hurdle for many CNC programmers. This error typically signifies that Windows cannot load the device driver for the hardware because it may be corrupted or missing.
The most frequent culprit in modern versions of Windows 10 and 11 is a security feature called Core Isolation (Memory Integrity), which can block virtual drivers from functioning. Step 1: Disable Core Isolation (Memory Integrity)
For many users, this is the definitive fix as modern Windows security often flags older or virtual drivers as unauthorized. Open the Start menu and search for Windows Security. Navigate to Device Security on the left sidebar.
Under the Core isolation section, click on Core isolation details. Toggle the Memory integrity switch to Off. Restart your computer to apply the changes. Step 2: Clean Reinstall of USB Drivers The "Error 39" associated with the Mastercam Virtual
If the security toggle doesn't work, your drivers may be genuinely corrupted. A simple update often isn't enough; a full removal and fresh install is recommended.
Uninstall via Device Manager: Open Device Manager, find the problematic device under Universal Serial Bus controllers, right-click it, and select Uninstall device.
Fresh Install: Download the latest official drivers for your Mastercam version or HASP key. Experts suggest using the latest manufacturer-supplied drivers to ensure compatibility with Windows 10/11. Step 3: Registry Fix (Advanced)
If the error persists, there may be corrupted "UpperFilters" or "LowerFilters" values in your Windows Registry that prevent the driver from loading.
Virtual USB Bus Error 39 usually occurs when Windows refuses to load the emulator driver (like MultiKey) required to run unauthorized or modified installations of Mastercam. This is typically caused by Windows security features blocking unsigned or incompatible drivers. 🛠️ How to Fix Virtual USB Bus Error 39 1. Disable Windows Memory Integrity
Windows security blocks older or unsigned virtual USB drivers via its core isolation feature. Turning this off usually solves the problem immediately.
Open Windows Security by searching for it in the Start menu. Click on Device security. Select Core isolation details. Toggle Memory integrity to Off. Restart your computer for the changes to take effect. 2. Disable Driver Signature Enforcement
Windows requires all drivers to have a valid digital signature. You can temporarily or permanently bypass this to let the emulator load.
Hold the Shift key while clicking Restart from the Windows power menu.
Navigate to Troubleshoot > Advanced Options > Startup Settings. Click Restart.
Upon reboot, press F7 or 7 to select "Disable driver signature enforcement". 3. Remove Registry Filters
Corrupted class filters can trigger Code 39 for USB devices. Deleting these keys often resets the driver status.
Press Win + R, type regedit, and click enter to open the Registry Editor.
Navigate to the following path:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\36FC9E60-C465-11CF-8056-444553540000
Look at the right panel for entries named UpperFilters or LowerFilters. Right-click them and select Delete. Restart your computer. 4. Delete Corrupt User Profiles
Community reports on the Google Groups Mastercam Forum suggest that hard program crashes can corrupt the active Windows user profile, mimicking driver errors. Log into a secondary administrator account. Back up your personal files from C:\Users\[YourUsername].
Delete the corrupted profile via Advanced System Settings > User Profiles. Recreate the profile and launch the application. Open Control Panel > Programs and Features
⚠️ Note on Software Licensing: The use of virtual USB bus emulators (such as MultiKey) is heavily associated with bypassing Mastercam's hardware lock (HASP) copy protection. To completely avoid security risks and OS errors, use an official software license with updated drivers directly from the Mastercam Support Portal. Mastercam X7-2022 Virtual Usb Bus Error 39 - Google Groups
Step 1: Download the Latest Sentinel Driver
Do NOT use the driver from your Mastercam X7 DVD. Go to Thales (formerly Safenet) and download the Sentinel LDK Windows GUI Setup (version 8.21 or newer). This single driver supports HASP (for X7) and LDK (for 2022).
Step 2: Uninstall All Old HASP/LDK Software
Control Panel > Programs and Features.Sentinel HASP, Sentinel LDK, HASP Driver, Mastercam USB Key Driver.Step 3: Clean Registry Leftovers (Important)
Win + R, type regedit, press Enter.HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ServicesHASP or Sentinel (e.g., HaspHL, Sentinel64). Caution: Do not delete anything else.Step 4: Install the New Universal Driver
Run as Administrator.Step 5: Plug in the Dongle
Insert your Mastercam X7 or 2022 dongle. Windows should now detect it as "Sentinel HL Key" without Error 39. Launch Mastercam.
Rating: 3/5
Error 39 (Windows Code 39) usually means:
“Windows cannot load the device driver for this hardware. The driver may be corrupted or missing.”
After a Mastercam update or Windows update, the Virtual USB Bus (often part of a license dongle driver, like HASP/Sentinel) can break.
Quick fixes:
The Mastercam X7/2022 Virtual USB Bus Error 39 is a classic driver conflict, not a death sentence for your license. With the updated Sentinel LDK universal driver and a methodical cleanup of hidden devices, over 90% of users can restore their USB key in under 30 minutes.
Always remember: Mastercam X7 was built for Windows 7, so running it on modern Windows 11 requires the legacy driver tweaks in Methods 1 and 3. Mastercam 2022 is far more robust, but still vulnerable to Windows update conflicts. Bookmark this updated guide for the next time a Windows update tries to break your CAM workflow.
Have you fixed Error 39 using a different method? Share your experience in the comments below to help the Mastercam community.
Disclaimer: This article is for educational purposes. Always back up your registry and create a system restore point before modifying drivers. Mastercam is a registered trademark of CNC Software, Inc.
Important Note: Mastercam X7 is legacy software (circa 2013). Error 39 usually means the HASP/Sentinel driver (the virtual USB bus that hosts the network license) failed to start due to driver signature enforcement or a corrupted installation.
Verdict: A Necessary Evil for Legacy Users The "Virtual USB Bus Error 39" fix is not a piece of software you review for features or aesthetics; it is a utilityReviewed as a survival tool for running legacy versions of Mastercam (specifically X7 through X9) on modern Windows 10 and 11 operating systems. While it solves a critical problem, it requires careful handling regarding system security.
Editing the Windows Registry is risky. Incorrect modifications can cause system instability. It is recommended to back up the registry before proceeding.