Two possibilities. The fw file you're using is unsuitable for the device or it's faulty which is why WU reports "The update file is corrupted", or the device is soft-bricked and you need to cure it so as to reenable Mass Storage Mode to delete any bad file(s). In this case maybe it's just gupdate.gcd file causing it not to boot. Look here: [Only registered and activated users can see links. ].