I think the first loader you gave me is the good one.
On the USB 2.0 ports of my Windows box I got the "Could not write device" error I showed before.
On the USB 3.0 ports the error is different:
Code:
Found EDL 9008
Could not open device
The different connectivity issues make me think that the cable is relevant. I have not been using the device's cable so far, but a different one. I think trying with the OEM cable could pay off.