UNO not powered/detected

I am having some issues with my Arduino UNO. For all the following I have used Windows based machines.

I have plugged it into several different computers with various cables and the UNO does not power on. On some computers, a Power Surge error for the USB port comes up. So presumably the device draws too much current and the USB port cuts out to protect itself.

I am able to attached an external power supply to get the ON LED to light continuous and the L LED to flash. Even so, when I connected the UNO via USB, the UNO is not auto detected (so updating drivers is a moot point since the computer doesn't see the Arduino at all).

Any clue what might be happening here?

hey im having the same problem with my uno so if you find whats wrong or even if its just fried can you please post it here

Eventually I figured out with some tinkering the problem was hardware.

One of the pins in the USB connector on the board had gotten bent. This shorted the USB voltage to ground. I was able to use some tweezers to pull the pin back into position. In my case, looking at the pins, it was obvious one of them looked funny.

Hey thanks it wasn't the USB but when I looked at that I relised I had a 5volt wire in the wrong place it seems to be working now :)