iDane: Did you solve your problem? I have the exact same problem as you. Back in Denmark with the iPhone with no service plan, the AT&T card is included but I can't activate.
What to do?
The current status is like alot of other people. Im awaiting the jailbreak (for firmware v. 4.1.) and the unlock (for baseband v. 02.10.04).
I hope that once the unlock is installed and my simcard will get connection to a mobile network, the phone will activate. I'll update this thread as it goes.
Concerning the jailbreak and unlock, I read on the official jb thread on this forum, and on twitter that it should be ready real soon. Hopefully the unlock will be done soon aswell.
All we can hope for is the dev-heroes that makes the jb and unlock keep ignoring those imbeciles who give them a hard time, for their own lack of patience. The jailbreakers and unlockers is doing great and much appreciated work, and we're lucky that they even bother. Some people should remember that.
I am in the same situation as you, but I'm wondering about the unlocking of baseband 02.10.04. Will it be available to unlock it with Greenpois0n? Or do we have to wait a little longer?