From reading the reviews of this product on Amazon I likely inserted the Molex connector in the wrong orientation into the converter.  Instead of the female-corded end being made of hard plastic, it’s made of soft rubber.  I didn’t even realize it was being inserted incorrectly because there was enough give in the connector to give the user a false sense of correct insertion.  Of course I can’t test my hypothesis as getting it wrong will result in another fried motherboard. Buyer beware.