Hi, my wife used her C91 Upgrade and give it to me today. It wont boot up. I only see Zenithink Boot-Screen and then a black screen appears. But with Backlights. So I try presing Vol+ and Vol- and Camera Button during bootup. Dont help. Then i download the latest firmware from Zenithink and put it on the SD-Card. Bootup doesnt work. Any Ideas? Sry for my bad english!