Did mine a couple of weeks ago in 1/2 hour stages with my engine running. I found that each 5% takes about 7 or 8 mins to complete. I also had a couple of hiccups while installing. Firstly an error message came up saying it couldn't continue the install and to re-insert disc even though like you I was installing via a usb stick. I turned off the engine removed and re-inserted the USB stick, started up again and it carried on from where it had stopped. The second problem was another message saying I was trying to install an older version, which I obviously wasn't. This time there was a cancel button to press and it again carried on installing. You would think with all the tech installed in these cars there would be an easier way to do this upgrade. If you haven't already done so I would pull out the USB stick, re-insert it, wait for about 10 mins and see if it continues. Hope this helps.