iPhone stuck at "No SIM card installed" I "retired" my old iPhone 3GS when I got my shiny new iPhone 4 and I was happily using it as an iPod touch with camera and compass.

However, I made the mistake of throwing away the SIM inside the 3GS, because I wanted to permanently disable any phone functions, and make sure I didn't have to turn on airplane mode or anything silly like that.

Well, that seemingly worked fine until iTunes upgraded the 3GS to iOS 4.0.2. Now the sim-less iPhone 3GS is stuck at ...


  No SIM card installed
  Insert an unlocked and valid SIM to activate iPhone




What sucks is that I can't figure out any way to get around this!

Apparently, based on the (excellent) How to Activate a Used iPhone the only way around it is to either


Jailbreak
Get an AT&amp;T sim, somehow


I tried to Jailbreak but I was nowhere near smart enough to navigate the maze of twisty passages involved in jailbreaking this 3gs. iBoot too new? ipsw not recognized? ... what?

I feel like an idiot now because apparently an AT&amp;T sim is REQUIRED to make an iPhone work even if you have no intention of ever using it as a phone? Is that true? How can you get around this "No SIM card" issue?
This is, unfortunately, expected behavior. Whenever you activate an iPhone (which you do as part of an OS install) it talks to Apple's servers and does various things like exchange crypto certs for APNS, etc. It also checks the IMEI of the phone to see what carrier Apple sold it to, and validates the SIM is valid for that carrier (if you buy an unlocked iPhone in a country where you can buy either locked or unlocked phones the vendor will actually copy down the IMEI number of a normal locked phone, and then enter in their system where it gets pushed to Apple's servers as an unlocked phone, there is no physical or configuration difference on the phones).

The easiest way to get it activated is (as you surmised) to use an AT&amp;T SIM. You mentioned you have an iPhone 4, you can activate it with that SIM. There are plenty of companies that sell microSIM to SIM adapters, but if you want to do it right now you can just place the micro SIM directly in the iPhones 3GS's SIM try with tape. I would not recommend doing this on a device you intend to keep the SIM in for a an extended period because the SIM is likely to come loose (and jam the SIM tray), but if you are just inserting it, activating it, and removing it you should be fine so long as you are pretty careful with how you apply the tape and not shaking the phone too much.