Hi Gabi, that is a tough one, sounds like a Beaglebone error/USB error rather something from our Chi.Bio operating system itself.
The fatal error often means the USB connection is not stable/was cut. Have you tried connecting it to a different PC and seeing if that solves it?
Just an update: I was able to make it work. It was indeed a cable problem. But I could only solve it when I changed the cable. The one that was purchased with the devide does not work at all.