I know so many people with lot of excitement upgraded their iPhone to OS 4.0 Beta1. After few minutes of discovering the new features you will realize most of your old application are crashing and not running as it is supposed to work. Many of my favorite applications did the same and I got really annoyed. I cannot really blame Apple for OS 4.0 as it is still in beta.
I decided to restore my iPhone to previous 3.1.3 firmware and I kept getting this annoying error 1015. After searching almost a day I found this method which helped me to get back to 3.1.3 firmware. I hope this will help you all
Step #1 Download and install the library “libusb”.
Step #2 Download and copy the application “iRecovery” to the desktop
Step #2 Open iTunes, click the ALT key + Restore and manually load the original 3.1.3 firmware.
Step #3 During the restore process, you’ll notice a pop up with error 1015, neglect it.
Step #4 Click Ok to close the pop-ups and close iTunes.
Step #5 Now open the terminal and type the following commands:
. /iRecovery -s
setenv auto-boot true
Step #6 Wait a few seconds and disconnect the iPhone from the cable, then reboot the phone by clicking Home + Power buttons simultaneously.
Step #7 Once you connect the phone via USB and proceed normally, the Apple logo appears on the display.
My sincere thanks to Chris Martin for translating this original article.