The battery just went out on our 07 Xterra and I brought it to the autoparts store that I work at to replace the battery. A fellow employee installed the battery and when I went to crank it over it cranked but did not fire. The security light was stuck on and neither key worked. I called Nissan North America and they said there was nothing they could do. A friend who works at the local nissan dealership took a look at it with the consult ii and sure enough it had a chain of immobility code and lock out code. He was not able to delete the lock out code or even reprogram the keys. So far his best explanation is a bad antenna that is not picking up the key. The part is on order and will be here tomorrow. I suppose I'll report back and let everyone know how that goes. If anyone has any other suggestions I would love to hear them because I would love to have our truck back.