Unplug everything from your computer except got the keyboard, mouse, and Iphone. Restart the computer. If using windows, disable your security software 100%. Try again. If that does not work, try a hard reset as explained here:
1) Turn off the iPhone. Make sure the USB male end of the cable is attached to the system. iTunes should be launched.
2) While holding the home button plug your iPhone in.
3) Follow the on screen instructions to a hard reset. This removes all data from the phone.
4) Try restoring oncemore