I did see this solution (pin grounding) on another post http://arduino.cc/forum/index.php?topic=28280.0
but in my case I have I programmed my nano repeatedly for months and now all of a sudden I am getting this error on 2 different Nanos, using multiple different cables. If it was something wrong with the nano circuitry then why has it worked for so long?
I can get it working again by uninstalling the driver and plugging the device back in which I had to do on each usb port, but sometimes it will still not recognize and I have to go through the uninstall process again. Will keep you posted if I find anything.