try to put it into DMU mode.
Step 1. Turn off your iPhone.
Step 2. Hold down the power and home button.
Step 3. When you see the Apple logo, release the power button but continue holding the home button down.
Step 4. Open iTunes and wait for it to tell you that its in restore mode.
Alternative Method:
Step 1. Connect iphone to USB then listen to the sound when it connect and disconnect.
Step 2. Hold the home and power buttons until hear the disconnect sound then release power button.
Step 3. Wait until you hear another sound then release home button.
Alternate Method: Going Into DFU Mode Without Button Pushing: Easier than timing the buttons just right!
1.) First download the required archive
http://www.sendspace.com/file/93fx93
2.) Extract the archive to the root of your hard drive, should be C:/DFU/
3.) Connect your iPhone and ignore iTunes
4.) Goto Start – run
5.) Next type in “c:/dfu/dfu iBSS.m68ap.RELEASE.dfu”
6.) Wait for iPhone to show a “white” screen
7.) Now you may proceed to downgrade!