Was a bit too quick here, found the solution for this. Using the power-button BIOS upgrade procedure brought the USB connection back to life.
- Press and hold the power button down for 3 seconds. Release it before the 4 second shutdown override.
On the other hand, has anyone managed to get the stick booting headless in "Ubuntu mode" ? It seems that it gets stuck somewhere, but i cannot determine where in the boot process. And if I reconnect the display after power-on, there is NO picture at all... And the operating-system does not boot, in example there is no connectivity through the USB-to-ethernet adapter.
I have only tried Ubuntu 15.04 with numerous different grub options, since the 14.04 Installer does'nt seem to recognize the mmcblk storage device out of the box.
15.04 isn't supported by the device, only 14.04 LTS 64 bit. I can say that version boots and runs just fine for me off a microSD card. Didn't try it headless though.