Recently, my sister got an iPhone 4s, which I have as well. Now, whenever I select her contact in my Messages app, the program immediately fails and my phone goes to the springboard. I've tried it both with iMessage turned on and off. Also, it does it no matter how I'm accessing the contact in the Messages app (both when I tap her name and when I receive a text and try to respond going directly from the lockscreen to her info. I can send texts using Siri though. I'm on 5.0.1, but the problem also existed when I was at 5.0. Any ideas on how to remedy this problem?