The "Virtual USB Bus Error 39" is a frequent driver signature and integrity issue that blocks Mastercam from detecting its software protection dongle. Windows prevents the driver from loading because it cannot verify its digital signature, resulting in a Device Manager error code 39. This updated troubleshooting guide provides systematic methods to resolve this issue and restore software functionality. Understanding Error Code 39 in Windows
A common scenario reported by users is that Mastercam was working perfectly until a mandatory Windows Update was installed. For instance, the Windows 10 update to version 20H1 rendered many Virtual USB Bus drivers inoperable. Similarly, Windows 11 upgrades are notorious for introducing new driver signing policies that break legacy compatibility.
An attempt to update the HASP driver may have failed, leaving behind faulty registry entries. Step-by-Step Fixes for Virtual USB Bus Error 39
The Virtual USB Bus driver is used to emulate a physical USB security dongle. Error 39 occurs when Windows security features block this emulation driver, or if the driver itself is outdated and incompatible with current Windows updates. mastercam x72022 virtual usb bus error 39 updated
If the Windows UI restricts you from toggling Memory Integrity, you can force it off via the registry: Press Win + R , type regedit , and hit Enter.
This is a known issue when using for Mastercam X7 (or older versions) on Windows 10/11 after certain security updates.
If you want to isolate the exact cause of your driver issue, tell me: Which are you currently running? Is this a local hardware dongle or a network-based license ? The "Virtual USB Bus Error 39" is a
This does not mean your files are missing. Rather, Windows is actively blocking the virtual device driver from injecting into the kernel because the driver lacks an updated, digitally verified signature compatible with modern Hypervisor-Protected Code Integrity (HVCI). Step-by-Step Fixes for Virtual USB Bus Error 39 Method 1: Disable Core Isolation (Memory Integrity)
: Search for "Windows Security" in the Start menu.
If the error occurred immediately after a Windows Update, you have two primary paths: Understanding Error Code 39 in Windows A common
The most common workaround to allow older virtual USB token systems to load is disabling the specific virtualization security protocol in Windows.
If you get an error stating the or "Windows cannot verify the digital signature" during Step 2 (even after disabling enforcement), you need a more direct fix.
Navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\36FC9E60-C465-11CF-8056-444553540000 . In the right pane, look for or LowerFilters . Right-click and Delete these values. Restart your PC. 3. Clean Reinstall of USB Drivers
The drivers used for the Virtual USB Bus emulator (often used for legacy installations or specific licensing models) frequently lack this valid signature or have signatures that have expired or been revoked by Microsoft. This is particularly true after major Windows security updates, such as KB5004237 . When Windows sees this unsigned driver, it classifies it as a security threat and blocks it, manifesting as Code 39. Consequently, Mastercam cannot find the license (HASP), and the software refuses to launch.
The Virtual USB Bus Error 39 can strike seemingly at random, but it usually has a specific root cause. Understanding these triggers is the first step toward a permanent fix. Based on community forums and technical support articles, here are the most common culprits: