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

This emulates the HASP and avoids Error 39 entirely.

This error is a specific driver conflict related to Windows Driver Signature Enforcement and outdated CodeMeter/HASP drivers. It is frustrating, but entirely fixable.

5. Resolution Strategy

The resolution involves manually removing corrupt registry keys associated with the device class to force a clean re-initialization of the driver stack.

Choose Troubleshoot > Advanced Options > Startup Settings > Restart. Step 3: Disable Enforcement