If your Jailbreak went wrong, or you installed an application from Cydia that isn’t compatible and you are stuck with the Apple Logo loading at infinite loop, meaning it doesn’t want to load to your lock screen. I might have a solution. This could happen on your iPhone 4 and any iDevices with iOS 4. Instruction Below:
1. Turn on your PC or Mac
2. Run iTunes
3. Get ready to connect the sync cable to your iPad, iPhone or iPod Touch
On your iDevices (Please familiarize yourself with the steps below before continuing):
1. Have your sync cable close to your iDevices
2. Plug the cable to your PC or Mac
3. Plug the other end to your iDevices
4. And quickly Press two buttons at once, the power and the home button
5. Let go of the power button but don’t let go of the Home Button
6. Now you will see an iTunes icon with a sync cable icon below it.
From here, follow the prompt in iTunes. Essentially you want to do a restore, so click on restore and sit back until all your stuff is reset to factory.