I apologize if this needs its own thread, but this seemed like a good place to go.
I have never done anything with a phone besides use it as it was intended. I got antsy and got Froyo. Unfortunately, the instructions I found did not mention removing the SIM card.
SO... The phone starts, but does not recognize the sim card, no matter what I do. I have my old Motorola Backflip, and it sees it just fine.
Do I just need a new SIM card from AT&T? Will that solve the problem, or am I S.O.L.?
For the record, I have put the sim card in when the phone is off, and when it's powered up. I don't know what else to try.
I would recommend using Odin3 and going back to 2.1. I can't think of any way to fix this issue. It sounds like your phone just completely had a loss of function when upping to 2.2.
I know, 2.1, why go back when you have 2.2? But trust me, the 2.2 that you have makes you hate this phone. It's got lag off the heezy, and it's just not worth it. I'm sure it'll get your phone to take the SIM again. If not, you have stock 2.1 update 1, and you can go cry to ATT or Samsung and get a new Captivate/a fix.