A little Update, i contact the Seller, they give me some Things to try incl to pull the Backcover and unplug the Battery (they said that is ok to scratch the warranty Sticker) and plug back in, but no respond from the 350 when its plugged with the USB Cable, green Light is on, but no working Device. They want to talk to the engineers and contact me tomorrow. I'll give you the infos, if you wanna hear it :-)