I had my arduino uno connected to an external 12V supply for 2-3 hours as I was working on other parts of my project. Suddenly the voltage from pin 9 which I was monitoring in the oscillator dropped down to 0 approximately. I went on removing the external supply. The board was very very hot. I then connected the usb to my laptop and I got an error 43 (windows did not allow the device to connect because it was reporting problems). I can't load any program of course. The 5V pin works but it outputs a voltage lower than usual(at about 3.9V).When I connect the external supply the 5V pin outputs full voltage. Any idea? Any fix?
PS: windows 8.1 x64