Problem, solved phew. Turn off the unit, hook up usb keyboard. Turn the unit again, during boot loop, press ALT+E+PrintScreen key repeatedly until scramble screen comes up. Then type in 'yes' in the scramble screen and press enter. It will continue with the upgrade process. The last stage where restoring system data not completed. Once this stage completed, it will notify upgrade completed and press OK.Anybody know how to fix the boot loop after upgrading. ?