Replaced broken screen now apps are jumbled
iPhone 3g screen was shattered so bought replacement kit and replaced it. After reassembling and powering up, it came on. However, if I try to access an app, it opens a different one. Also some of the apps at the very bottom won't work at all. Iftrying to text, it doesn't display the character typed but a random one. What could be wrong and how do I fix it?