Please do not listen to someone that isn't a experienced jailbreaker. Now do you have any kind of SBSettings type app like UISettings, PowerCenter, etc,etc that is on the notification center that will let you reboot in safe mode. You need to reboot your phone in safe mode and than delete the last app you installed. And everything is fine. Post this stuff in the jailbreak forum so your not getting guys who aren't experienced at jailbreaking responding. At least 4 people in this thread have no idea what they are talking about. Me, Massie, etc have experienced the 1/4 screen issue and fixed it without a restore.The problem you have people are experiencing with SBSettings and Winterboard. Download a notification center app that has a respring and safe mode option on it. There are around 3 or 4 of them. I recommend PowerCenter and it is available at cydia.wrightscs.com . Add that repo in Cydia under Sources - Edit - Add . This way you have a safe mode reboot option that will reboot the phone in safe mode and allow you to uninstall a non ios5 compatible app. If you have anymore questions fill free to post in jailbreak forums or ask me or Massie, etc. Number of people that can help you.