The Precision rebooted. No yellow exclamation. The virtual USB bus showed as "running" in Device Manager. Marcus launched Mastercam X7.
If Error 39 keeps returning, abandon the virtual bus entirely: mastercam+x72022+virtual+usb+bus+error+39+fixed
The answer is . Microsoft has aggressively tightened driver signing requirements (SHA-2 and HVCI). Older Virtual USB Bus drivers (circa 2013-2019) are unsigned or use weak signatures. When Windows updates, it often: The Precision rebooted
If you're seeing "Windows cannot load the device driver for this hardware... (Code 39)" in your Device Manager, try these steps to get back to work: mastercam+x72022+virtual+usb+bus+error+39+fixed