Could you open up the Windows Device Manager and check to see if the Leap Motion Controller shows up under USB devices or imaging devices?
Does the green LED on the side of the device turn on when it's plugged in? If not, it sounds like it may be a firmware issue. Please try downloading and running the firmware reset tool from here: https://leapmotion.box.com/s/9duyevo5wbfjgh1kicn4
If you're prompted to enter a key, press enter and it should proceed with the reset process.