O.K. this is primarily for a bad flash / corrupted NAND.

Personal experience: Fixed 3 times without opening jtag up

Requirements: Original NAND, USB stick(any size even 256mb would do), ability to boot into xell.

Start with your jtag off + HDD taken out

1) Put your original nand(would be called freeboot.bin / flashdmp.bin) onto your usb stick, and rename it updflash.bin . Delete everything else off your usb stick.

2) Plug into jtag

3) Boot into xell by pressing eject(your disk drive has to come out, mine is fault and I have to nudge it a little).

4) Let it to all the processes, make sure everything is complete(give it about 3 minutes), then unplug the power from the back. The disk drive should stay open.

5) Wait 30 seconds minimum.

6) Plug power back in, and press eject(disk drive should still stay open).

7) Let it do all its processes(another 3 minutes maybe).

Turn off normally by the power button. Wait for it to completely shut down(fan stop + disk drive doesn't spin) - The disk drive should close whilst turning off

9) Unplug EVERYTHING from your jtag; internet, AV cable, power, usb stick.

10) Wait 60 seconds minimum

11) Plug all back in(including HDD) and it should work by turning on normally