app crashes after default screen loads. but only in 4.0

I am a newbie working on my first app. I have successfully built an app that needs a few minor changes in 3.1.3. Can I upload the app to Apple in this build or do I need to port it over to 4.0. Because when I port it over to the 4 sdk, it crashes right after launch. It's开发者_JAVA技巧 a simple mad libs type of app with animations. I have been pouring over the code to see what is different between the two sdks and I see nothing. I copied the code from 3.1.3 to 4. do you think that is the problem. I did this to save time in retyping it. Please help.

You need to submit with the 4.0 SDK now.

When an application crashes, it either leaves a traceback in the log (open the XCode log window), or you can attach the debugger and see the crash point.