Hi, I just bought this used iPhone 3G today and it worked with my own T-Mobile SIM card for a couple of minutes before I let iTunes perform a software update to bring it from IOS 4.0 to IOS 4.2.1. After the update, I am stuck on a boot-up screen that says: "Insert a valid SIM with no PIN lock" and it won't accept my T-Mobile SIM (not surprisingly). Is there a way to get past this? I read about using the iPad's firmware (6.15.x) on my iPhone 3G, but I'd rather not do that. Is there another option?