Turn off Airplane Mode before updating your iPhone firmware

I finally updated my iPhone to 2.2.1 today, and after a reboot I got the screen that says it needs to verify or authenticate the SIM card. Unfortunately, that failed because, while I do have a SIM card in there, I do not have AT&T service -- and I had the cell radio turned off. My iPhone is never used as a phone (I don't have T-Mobile in my area, so even unlocking it would be useless). I wound up restoring the iPhone, which took a couple of hours, but apparently there's a better way.

Danny Goodman on the Apple Discussion boards posts this "2.2.1 Upgrade and SIM Error (and Solution)" tip. My advice? Always turn off Airplane Mode before applying a firmware update. The phone wants to access the radio hardware during the upgrade, it seems, and disabling the cell radio makes this impossible. Thus, I was locked out of my phone for several hours today. As luck would have it, I stumbled upon this tip about 5 minutes after I started the restore process.