Do this to restore your iPhone:
Just open iTunes...Hold the Power and Home button until it says to connect and then connect it. Then it will ask you to restore. Close that dialog box in iTunes and hit restore.
When you Jailbreak and use iPhoneInterface, your iPhone is unlocked. To lock your iPhone back you need the file "Services.plist". After you have made all of your mods in iPhoneInterface, before you quit & undock, you need to:
This allows the iPhone to lock itself back, in essense, making it detectable again by iTunes.