I've tried to install iOS 4.3.1 on my iPhone 3GS. Then I downgraded it to iOS 4.2.1 coz 4.3.1 was not being signed and I think I dont have it's SHSH blobs saved. So, after downgrading to 4.2.1, I jailbreaked it with redsn0w. After the jailbreaking process, it is asking me to insert a vaild SIM to activate it which I dont have. I even tried to jailbreak it with Greenp0ison but it shows me the same error. It was working fine earlier on 4.2.1. Plz help me guyz, thanks.