Ok, i switched to a Lexar JumpDrive Firefly 8G, and it worked the first boot. After that Uboot stopped at
Somewhere I should have another Sandisk drive, maybe that one works.
USB: scanning bus for devices... 3 USB Device(s) found Waiting for storage device(s) to settle before scanning... TAlso no luck with a Sandisk Cruzer Edge, same issue as with the Intenso.
Somewhere I should have another Sandisk drive, maybe that one works.