What you could do (maybe, im not familiar with the 3g, as I have a 2g...) is simply downgrade (using winpwn or pwnage tool) from 2.2 to 2.1. Someone correct me if I'm wrong, though!
Also, I am thinking about getting a 3g. I have a 2g unlocked with tmobile. And I want to have a 3g so that when the dev team comes out with the soft unlock, BAM! I'll have it. Could anyone tell me (if you have gone from a 2g to 3g on tmobile) if there is really any difference? I know tmobile can't use 3g because that whole different frequency thing, but who knows, maybe things will change? Maybe thats hoping for too much.
lol
Good luck with your problem though! I hope you get it fixed! If not, you could always restore it and take it back to the apple store and say it wouldn't connect to itunes or something. They will test it and then say I have two macs and two pc's, It still wouldn't connect and they'll give you a new one (which you can only hope to be on 2.1.
Oh, and can I ask where you got a 3g? Did you decide to pay for service and cancel making the 300 dollar phone now cost 500-600 with all those fees? Or did you know a guy, who knows a guy, who knows this place where there is a group, who knows another guy, whose friends with a girl whose boyfriend knows a guy who 'found' a shipment of iphone 3g????? don't worry, i'm not the fbi, I just want a 3g for cheap lol..