Finally someone else with the problem. I made a thread about this on the Iphone 5 launch.
I believe this to be an activation bug that only affects iphone 4S on ios6.
Here is my story:
Bought iphone 5 on launch day. Took my 4S which was updated with ios6, and did a factory reset on the device through settings. I hand down my iphones to my fiance when i get the new one.
I took the sim out of her iphone 4, put in in the 4S. Went through the set up process. When it got to the 'activation' screen, i got an error message that i needed to insert a sim card that corresponds to the carrier, or visit my carrier for a new sim.
This made no sense, since my fiances sim was of course an at&t sim, and this was an at&t 4S.
I tried turning off/on the phone a million times. Tried my old, deactivated sim. Nothing. I plugged it into itunes to re flash io6. Itunes gave me the same message and didn't let me do ANYTHING whatsoever. Not even restore.
I had to do a dfu restore to re flash. That did absolutely nothing to fix the problem. I did this 3 more times.
Finally i went to the at&t store and got her a brand new sim. This also didn't help. WTF!
At this point, i'm pretty pissed off, thinking....what the HELL kind of sim card does this damn phone want if not an at&t sim?? I had a t mobile micro sim i used in her old 4 which was factory unlocked. that didnt work either.
I called at&t tech support. The guy told me that i had to have a 4G micro sim to activate. This made no sense to me whatsoever. But i kind of went along with it since the my micro sim i had in the 4S while i was using it looked a little different than the brand new one i just got my fiance.
Meanwhile, i can't find ANYTHING on the internet about this problem.
The next morning, i went to an at&t store, explained what happened, and was told that there is no such thing as a 4G micro sim. He said they're all the same. But, issued me a new one anyway. We tried activating it there at the store. Nothing. He took his sim out of his 4S, and tried to activate mine. NOTHING.
Finally, a couple hours later, i went to the apple store. Explained the deal. And the genius was totally dumbfounded. He tried numerous "test" sims, did a dfu re flash, NOOOOOOTHING.
So he swapped my 4S. The one he brought out still had ios5 on it. It activated immediately.
Right before i was about to leave, i asked him if he could flash ios6 on it for me so that i didn't have to. He said sure.
He flashed it and then turned around and said, "you're not going to believe this". it didn't want to activate again.
I guess since it was new, it had to go through the setup/activation process.
He called more techs over, and they were all mystified.
i told them it's got to be a bug in ios6. they all agreed.
I got ANOTHER replacement. This one also had ios5 on it. Activated no problem.
And thats where i left it.
I'm sure if i were to go into settings and do the over the air update like i did when i was using the phone, ios6 would be fine. But she doesn't care about that anyways, I'm buying her the galaxy note 2 when it comes out lol.
Moral of the story, there is definitely something up with the 4S + ios 6 + setting up as a new phone and activating.
i didn't have any problem with her old 4 that i reset a zillion times on ios6 trying to duplicate the problem. even with an inactivate sim.
Major pain in the ass problem.