Originally Posted by
fullboat2
Not sure if this helps or not, but I just brought my AT&T phone to Saudi Arabia. I did the same preserved baseband/jailbreak/unlock you did. First time I put in new micro-sim I got same thing, Invalid SIM. I restarted the phone and it fixed the problem. Later in the day I rebooted the phone and got the Invalid SIM message again, rebooted once DID NOT FIX, rebooted a second time and it cleared up.
I'm half afraid to restart my phone! My SIM was locked and I disabled the lock the second time and it rebooted fine. Not saying that will fix it, but you're not alone, I had the same problem...