I bought a 2nd hand iPhone in Canada and moved to Thailand and ditched the original Rogers SIM card. I've tried a local SIM card but the error message "The SIM card inserted in this iPhone does not appear to be supported" appears in the iTunes dialogue box. I tried jailbreaking my phone with the brand-new Greenpoison release but failed - after the jailbreak hung up at a point in the process the phone rebooted with the same "plug me into iTunes / slide for emergency" screen. So my questions are:
1. Is it possible to jailbreak an iPhone (3gs, 4.1 firmware) with no SIM in it, or with an invalid SIM in it?
You can jailbreak no problem.. The issue you have is you need to unlock to use a diff carrier sim card. There is no unlock for firmware 4.1 so you'll just have to wait.