Hey Hasse
Try again to downgrade...first with v3.00, than to v.4.00.I had the same problem.Copy the OS in the Midjay root,shut it off, than after you start it up..you'll have a screen like.."Found new OS...." just push "enter" and let the machine to do all the mambo-jumbo.You don't have to push anything else,becouse the OS is going to flash-memory anyway!
Also , if want to push, afterwards, those 1,7..something to rewrite the flash-memory, push the buttons long enough till the screen apears.Just push them long...
Hope it helps,