To force restore your iPhone, enter DFU mode as shown below:

Connect the device to your computer and launch iTunes
Turn the device off (hold down the power button and home button at the top of the device)
Hold down the sleep/power button and home button together for exactly 10 seconds, then release the power button
Continue to hold down the Home button until a message appears in iTunes telling you an iPod in recover mode has been detected

Så gjenopprett og jailbreak på nytt.