I had a MBA for about 2 months now and a 1TB HD that is hooked up to the Extreme router. Just bought a mini and was trying to do back up. Set up the time machine to back up to the 1TB HD. The time machine logo is spinning (backing up), but it has being doing that for 24 hr?? And the status is always "preparing backup". So I hook up the HD straight to the USB of mini, but still the same,.... what's wrong?