Fix “Different SIM Detected” Problem in iPhone 4 / 3GS / 3G After Jailbreaking with JailbreakMe

JailbreakMe has to be hands down the easiest jailbreak method ever, but since it uses userland exploit like Spirit, it doesn’t hacktivate phones. iPhone dev and hacker named Sherif Hashim came up with a way to activate phones without having the original SIM cards but now it seems like Apple has found out about the phonebook SIM card trick and they have blocked it. And so if you activated your phone using phonebook SIM card, you will be getting the dreaded “Different SIM Detected” error on your lockscreen as shown in the screenshot below.

Follow the steps below to fix this problem.
Step 1: Restore to original iOS 4.0.1 from iTunes.
Step 2: Activate your phone by using phonebook SIM card as shown in the video posted below.


Step 3: Follow the step by step guide posted here to jailbreak your iPhone 4, 3GS and 3G using JailbreakMe 2.0.
Step 4: Now unlock your iPhone 4 .
Step 5: Now replace the phonebook SIM card with your unofficial / unsupported carrier SIM. It is now that you will receive the “Different SIM Detected” error.
Step 6: Download i-FunBox for Windows from here.
Step 7: Connect your iPhone with you computer and let the i-FunBox software detect your phone.
Step 8: Now navigate to /private/var/root/Library/ and delete the original lockdown folder as shown in the screenshot below.

 
Step 9: Now simply download the patched version of lockdown folder from here, and place it in the same location you deleted the original from: i.e. /private/var/root/Library/
Step 10: Restart your iPhone.
Your phone should now work normally again!