android - Unfortunately myapp has stopped

I am getting Application has stopped. The project changes scene to MainAplication to JobList but, Job List to ExerciseList, ı am gettin these "Unfortunately application has stopped." on emulator.Here is my classes. I am also gettin FATAL EXCEPTİN on logcat.

ApplicationMain.java

    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;

    public class ApplicationMain extends Activity {
/** Called when the activity is first created. */

EditText nameEditCtrl;
Button btnCtlr;
String name;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    nameEditCtrl = (EditText) findViewById(R.id.editText1);
    btnCtlr = (Button) findViewById(R.id.button1);

    btnCtlr.setOnClickListener(new ButtonClickHandler());
}

public class ButtonClickHandler implements View.OnClickListener {
    public void onClick(View view) {
        if (nameEditCtrl != null && nameEditCtrl.getText().length() != 0) {
            name = nameEditCtrl.getText().toString();
        } else {
            name = "Guest";
        }

        Intent intObj = new Intent(ApplicationMain.this,
                JobList.class);
        intObj.putExtra("USERNAME", name);
        startActivity(intObj);
    }
}
 }

JobList.Java

    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.ImageButton;
    import android.widget.TextView;


    public class JobList extends Activity {
TextView greetMsg;
ImageButton ib;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.joblist);
    greetMsg = (TextView) findViewById(R.id.textView1);

    Intent intename = getIntent();
    String uname = (String) intename.getSerializableExtra("USERNAME");
    greetMsg.setText("Welcome " + uname);



    ib = (ImageButton) findViewById(R.id.imageButton1);
    ib.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            Intent intObj = new Intent(JobList.this,ExerciseList.class);

            startActivity(intObj);
        }
    });





    }


}

ExerciseList.Java

      import android.app.Activity;
      import android.content.Intent;
      import android.os.Bundle;
      import android.view.View;
      import android.widget.Button;

      import android.widget.EditText;
      import android.widget.ImageButton;
      import android.widget.TextView;


     public class ExerciseList extends Activity {

ImageButton iz;

@Override

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.exerciselist);

    iz = (ImageButton) findViewById(R.id.imageButton2);
        iz.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {

            Intent intObj = new Intent(ExerciseList.this,
                    ApplicationMain.class);

            //intObj.putExtra("USERNAME", name);
            startActivity(intObj);
        }
    });


}
 }

AndroidManifest.xml

 
 package="com.prgguru.android"
android:versionCode="1"
android:versionName="1.0" >








    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" >
            android:name=".ApplicationMain"
        android:label="@string/app_name" >

        
            

            
        
    
            android:name=".JobList"
        android:label="@string/app_name" >