I have a theory on what is causing this error. @daniele1962 Does your led blink slow, or fast when powered on?
Can you try flashing Skylark with a Linux host? Or extract the .iso from the .ova file with 7zip and either burn the .iso to a disk or make a bootable flash drive.
I think the problem is the USB drivers in windows. I have yet to see this error on a Linux box.