If I could add a comment...
I don't think step 6) above is quite accurate:
6. Press and hold the On/Off button and right arrow key simultaneously until the jetBook logo appears on the screen.
I tried doing the upgrade three times without success and couldn't figure out what I was doing wrong. I then looked at the 'official' instructions on www.jetbook.net
and noticed that it says wait "till the picture will appear on the screen."
I thought this might mean something other than the Jetbook logo, and indeed it is. When I kept the buttons held down for several seconds past the Jetbook logo, I saw a warning message asking me to confirm that I wanted to do a firmware upgrade, and I was forced to select either OK