Invalid "UpperFilters" or "LowerFilters" values in the Windows Registry can cause Code 39 errors. Step-by-Step Fixes for Virtual USB Bus Errors 1. Disable Core Isolation (Recommended for Windows 10/11)
Features like Memory Integrity can prevent the virtual USB bus from loading.
Download the latest from the Thales Sentinel Support Page. mastercam x72022 virtual usb bus error link
Windows often blocks virtual drivers through its "Core Isolation" feature. Open the and search for Windows Security . Go to Device Security > Core isolation details . Toggle Memory integrity to Off . Restart your computer and check if Mastercam launches. 2. Clear Registry "UpperFilters"
Enter the path to the virtual USB driver (typically found in your Mastercam installation directory). Restart your machine to apply the changes. Summary Troubleshooting Table Target Issue Primary Action Windows 10/11 Security Turn off Memory Integrity in Windows Security Registry Edit Driver Corruption (Code 39) Delete "UpperFilters" in regedit Driver Signature Unverified Driver Blocks Use DSEO to sign virtual driver files Clean Install General License Errors Uninstall old MultiKey and run latest install as Admin Download the latest from the Thales Sentinel Support Page
Modern Windows versions (10 and 11) block unverified virtual drivers for security.
Navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{36FC9E60-C465-11CF-8056-444553540000} . Go to Device Security > Core isolation details
If Windows continues to block the virtual driver, you may need to disable signature checks temporarily. Run the tool. Enable Test Mode and select Sign a System File .
In the right pane, find or LowerFilters . Right-click and select Delete . Restart your PC. 3. Reinstall Official Drivers
Before attempting third-party "patches," ensure the official Sentinel HASP drivers are up to date.