Here's some more info you might need:
Regarding the security light being on:
So if you lock the doors it should turn solid for 20 seconds then blink. But what I want to see is when you turn the ignition on, if that comes on solid. When the Nats is not active, the security light would be off when the key is in the ON position. That means the computer can't read the chip in the key. So the only thing they by passed is the steering lock release so you can turn the ignition on, but it's still unable to read the key. If uprev truly disabled nats then the security light would be off, since it's not off, it's active IMO.
BCM/NATS Reprogramming:
Well if you can find a mobile tech or something that programs keys, a Nissan Tech can decode the BCM 5 digit pin. So if you have the proper 4 digit pin they normally can program. What makes most outside techs not able to program keys is the software and the fact they can't decode the BCMs number since the Nissan database does this.
If you can get the 5 digit number off the top of the BCM then a Nissan tech can decode it for you. It would look like this;
http://www.carmod.net/images/altima/bcm-code.jpg
If it's on the BCM it would be here on the stick. If not there, then the scanner will need to pull the pin.. If you're unable to do this with the UpRev software then you will have the numbers from me so a mobile tech can do it if they have the software (consult 3 & security card) to program the keys.