I am having a very unusual problem with my iPhone, one that I cannot find any other posts about.
I unlocked/jailbroke my 2G iPhone into 2.2.1 using QuickPwn for Windows. Everything worked fine.
I then went to sync it with iTunes on my MacBook (I cannot run QuickPwn on my Mac because of the DFU mode update in Leopard). I sync it and everything appears fine. But almost immediately after the sync is finished and I disconnect my phone, I lose service. It displays "searching" and then eventually says "No Service."
I have tried taking my SIM card out and replacing it (I even got a new SIM card from my carrier. I also tired resetting the Network settings and rebooting the phone. No luck with anything.