So here's the deal, I've got me an iPhone 3Gs and I want to unock it for T-Mobile. I'm running OS X Snow Leopard, and want to run 4.2.1 or higher on the phone. I've tried limera1n and it didn't work, and I also tried redsn0w. All to no avail. I continuously land on the No SIM screen, and don't know what I'm doing wrong. Whenever I try to add a build through iTunes, it just says "Not eligible for the requested build." Help please!