My USB port wont work and computer is almost brand new

I have plugged in my iPhone 4 and synced it with my Macbook Pro when I first got it, now when I just tried to plug in a iPhone 5 it says there is a USB device already plugged in taking too much power and once it is unplugged my other USB devices will start working again. Problem is there is nothing plugged into my computer. I have tried command+option+esc but it shows nothing. I restarted my computer and then shut it down and started it back up again and it still tells me the same thing.