I used redsn0w 9.14b2 to do the JB on my iPhone4 (iOS 5.1.1), and that seemed to go fine. I then did a restore to the phone from the previous backup = original AT&T/Apple configuration. Next I did the "authorized" unlock through AT&T, and then tested the phone on T-Mobile, life's good.
The question is if I re-run the redsn0w JB again can that kill the unlock? I don't think that it will touch the modem firmware (04.12.01) that I'm running. I'd like for someone with more JB experience to confirm my sanity, please.
My goal is to have a permanently unlocked iP4 with the latest SW.