PS- gameowar- Make sure your battery has some power in it or it won't go into update mode.

Oops just realised I forgot to mention that you need to plug your phone into the PC, holding the U button before you run that flasher command



EDIT_ Just tried rebooting again and it will let me load nitdroid without having to do anything extra, so it's just the power kernel that needs sorting out on multiboot. That's no biggie, as I only installed it recently and hadn't even played around with it yet except to experiment what it was like at a setting of MAX: 805 instead of 600. It DID seem a nicer experience though, so I will try again soon I am sure.