You TSOP (the original BIOS) got screwed...
Maybe you tried to flash withouth unlocking the bios (i did it to my 1st box)
there's a way to fix the problem, check the tutorials to repair buggy tsops with matrix
(be warned... you need to solder several points to do so...)
I hope you still have the backup dir with you original TSOP.
And remember, live is banning xbox & hd serials that aren't the same.
So, If you're trying to unban you X, I think you can't, because is black listed...
Get a new console, they're cheaper now =)
Saludos