Normally we face This Problem that after restore, Itune ask for Orignal Sim to activate............ Solution is simple for 3.1.2
1. After update to 3.1.2 just Jailbreak with Blackrain
2. dont Run blackrain.... just "Restore" with Custome Firmware
3. Iphone will show same not activated Screen.
..........Don t Worry
4. Run Install.bat ...........open Itune.......wait...
Yes......your Iphone is Activated Now............Juz CHILL
Regards,
ALVI