Navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\36FC9E60-C465-11CF-8056-444553540000 .
Locate the item with a yellow exclamation mark (e.g., Virtual USB MultiKey , Virtual Usb Bus , or SafeNet HASP ).
Error 39 on the Virtual USB Bus is stubborn but not fatal. If none of the above works:
Common causes (specific to Mastercam licensing/dongles and virtual USB)
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.