It's likely I'm missing something obvious, so thanks in advance if you help me figure this out... Quick background: I've JB/unlocked 2 original iPhones in the past, never an issue. I've JB/unlocked my own 3GS, on 4.0.1. I've also JB/unlocked...jeez, let's see now...6-7 different iPhone 3G units for several different people. Always works, first time. Until today. Got handed a white iPhone 3G, 16GB. The original SIM was inside, to the best of my knowledge. The user has an iP4 now, so I'd guess the SIM was deactivated when the iP4 was "switched on." Fine, been through this before. Never had a problem using the Pwnage Tool, redsn0w, Spirit, or jailbreakme.com. This iPhone 3G is on 3.1.3. I am able to jailbreak using jailbreakme.com, but NONE of the other methods I've used have worked. Even when I do JB 3.1.3, I can NOT upgrade to 4.0, 4.0.1, or 4.0.2 (yes, I know a 4.0.2 jailbreak isn't advised). No matter what I try. Tried 3 different Macs, all latest version of iTunes installed. Nothing. Sure, I can JB/unlock 3.1.3 & be done. But I'm perplexed as to why no matter what I try iTunes simply won't let me upgrade this iPhone from 3.1.3 to anything else. I always get some message about how "this firmware isn't able to be installed on this phone." I've Googled it, and there are a TON of instructions on how to go backward from 4.0-->3.1.3, but not forward. Tried DFU mode also. The firmware upgrade goes the farthest this way, but never completes...I get the -1xxx error message or the aforementioned "this firmware doesn't work on this phone" message. Is the only way to get an upgrade to work is to temporarily borrow a working regular-sized AT&T SIM? I'm stumped.