I had the NAT error message at first, but I followed the on-screen instructions & it no longer says i have the NAT error. However, now I have these codes:
w: 0000 - 000B
x: 0000 - F001
y: 20A8 - 48E0
z: 0000 - 0000
I just got my 360 working again after having the RRoD for the last 2 years. Don't know if that matters.