OK, everybody, here is the solution!!
I know many people are looking for help, many people are waiting for help, YES, here is the solution.
Here is the complete instruction to downgrade iPhone from 2.2.1 to 2.2
1. Just open your iTunes,
2. Press “Shift” and click on Restore
3. Select “iPhone1,2_2.2_5G77_Restore.ipsw”
4. Waiting for restore
Now, after you restore, you will see 1013 or 1016 error on your PC(Not sure on MAC), at that time “DO NOT” disconnect your cable,
5. Open QuickPwn and do the instruction as QuickPwn says,
6. Select “iPhone1,2_2.2_5G77_Restore.ipsw” again for QuickPwn,
7. Follow the standard QuickPwn procedures and finish the process.
After QuickPwn shows complete, you may restart your iPhone.
At this point, your iPhone may work correctly and back to 2.2 successfully. However, your iPhone may turned on but no carrier signal, here is the following steps,
8. Open iTunes again,
9. Press “Shift” and Click