I am not sure if this will work for you but it worked for me. I am a mac user and I did this using itunes version 7.5. When attempting to downgrade from firmware 1.1.2 to 1.1.1 in itunes do not download the restore file (Iphone1,1_1.1.1_Restore.ipsw) using the safari web browser. Download the file from Mozilla Firefox instead. Then downgrade using one of the many guides available. Good luck!