The error can be caused by a variety of factors, including:
Hold down the while clicking Restart in the Windows Power Menu. Your PC will reboot into the blue Choose an option screen.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\vusbbus mastercam+x72022+virtual+usb+bus+error+39+fixed
: Always run Mastercam setup tools with administrator privileges to avoid local security policy restrictions.
: Major Windows feature updates can re-enable Memory Integrity automatically, causing Error 39 to return. The error can be caused by a variety
The Windows Device Manager reports Error 39 when it "cannot load the device driver for this hardware... the driver may be corrupted or missing." In the context of Mastercam emulators, this usually means or Windows Driver Signature Enforcement is blocking the unsigned virtual bus. Step-by-Step Fixes
Error 39 often persists due to stale registry data. : Major Windows feature updates can re-enable Memory
Navigate to: HKLM\SYSTEM\CurrentControlSet\Enum\USB\<virtual_bus_instance>\Device Parameters
"The issue is almost always Windows 10/11 security. If you don't turn off Memory Integrity in the Windows Defender settings, the virtual bus will never start, no matter how many times you reinstall it."