I have been using a USB (Male to Mini ) wire for my Nano for a few days. But suddenly, the cable doesn't seem to work with my Nano anymore. When I plug in to the computer with the cable, Windows says that the it couldn't recognise the device and that the device could be malfunctioned. My computer could detect the device again when I change to another USB cable.
So, for a while, I thought the USB cable is damaged even though I don't know how it just got damaged on its own. Later I tried using the USB cable on another device like a camera, my computer could detect the camera! The cable is still working! It just doesn't work with my Nano suddenly.
well this can happen; the arduino seems to be kinda sensitive for serial connections, and no one seems to know why. You can use a multimeter to test your USB-cable, but as you stated it worked on other devices, your cable is fine! There are a couple of people who happened to have the same problem, but there is no fix for this (AFAIK). So as long as you are sure you had your setup correct when using your "broken" cable, just stick to the cables that work.
To answer your question, you could have had some wiring connected to your tx and rx pins while using the "broken" cable. Your nano could have been sending serial data while your OS were trying to establish a connection. I am not very much into drivers so this info might be a little vague; sorry.
My Nano is connected to my computer through a USB cable. I'm using Processing, and so the sketch loaded onto Nano is the firmata. I need to have the board connected to the computer to run anything since I'm using Processing to communicate via the serial.