Excepción en las preferencias de lista

Esta es mi primera aplicación para Android y me he encontrado con una excepción al intentar usar la ListPreference. La aplicación se carga junto con las preferencias... pero cuando toco la entrada ListPreference las aplicaciones "se detiene inesperadamente".

Ajustes.java

public class Settings extends PreferenceActivity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.addPreferencesFromResource(R.layout.settings);
    }
}

Ajustes.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen
xmlns:android="http://schemas.android.com/apk/res/android">
    <CheckBoxPreference
        android:key="chk_enabled"
        android:summary="SMS response based on settings"
        android:title="Enable"
    />
    <ListPreference
        android:title="Contacts"
        android:summary="Contacs that will be sent SMSs"
        android:key="list_contacts"
        android:defaultValue="0"
        android:entries="@array/list_entries"
        android:entryValues="@array/list_values" 
    />
</PreferenceScreen>

Matrices.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="list_entries">
        <item>All</item>
        <item>WhiteList</item>
        <item>BlackList</item>
    </string-array>

    <integer-array name="list_values">
        <item>0</item>
        <item>1</item>
        <item>2</item>
    </integer-array>
</resources>

Esta es la salida de logcat:

D/AndroidRuntime( 3187): >>>>>>>>>>>>>> AndroidRuntime START <<<<<<<<<<<<<<
D/AndroidRuntime( 3187): CheckJNI is OFF
D/AndroidRuntime( 3187): --- registering native functions ---
I/jdwp    ( 3187): received file descriptor 16 from ADB
/ddm-heap( 3187): Got feature list request
I/ActivityManager(   86): Starting activity: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=tml.UI.main/.MainActivity }
D/AndroidRuntime( 3187): Shutting down VM
D/dalvikvm( 3187): DestroyJavaVM waiting for non-daemon threads to exit
I/ActivityManager(   86): Start proc tml.UI.main for activity tml.UI.main/.MainActivity: pid=3194 uid=10039 gids={1015}
D/dalvikvm( 3187): DestroyJavaVM shutting VM down
D/dalvikvm( 3187): HeapWorker thread shutting down
D/dalvikvm( 3187): HeapWorker thread has shut down
D/jdwp    ( 3187): JDWP shutting down net...
D/jdwp    ( 3187): +++ peer disconnected
I/dalvikvm( 3187): Debugger has detached; object registry had 1 entries
D/dalvikvm( 3187): VM cleaning up
D/dalvikvm( 3187): LinearAlloc 0x0 used 676380 of 4194304 (16%)
I/jdwp    ( 3194): received file descriptor 10 from ADB
D/ddm-heap( 3194): Got feature list request
W/Resources( 3194): Converting to string: TypedValue{t=0x10/d=0x0 a=-1}
I/ActivityManager(   86): Displayed activity tml.UI.main/.MainActivity: 977 ms (total 977 ms)
D/AndroidRuntime( 3194): Shutting down VM
W/dalvikvm( 3194): threadid=3: thread exiting with uncaught exception (group=0x4001da28)
E/AndroidRuntime( 3194): Uncaught handler: thread main exiting due to uncaught exception
E/AndroidRuntime( 3194): java.lang.NullPointerException
E/AndroidRuntime( 3194):    at android.preference.ListPreference.findIndexOfValue(ListPreference.java:169)
E/AndroidRuntime( 3194):    at android.preference.ListPreference.getValueIndex(ListPreference.java:178)
E/AndroidRuntime( 3194):    at android.preference.ListPreference.onPrepareDialogBuilder(ListPreference.java:190)
E/AndroidRuntime( 3194):    at android.preference.DialogPreference.showDialog(DialogPreference.java:291)
E/AndroidRuntime( 3194):    at android.preference.DialogPreference.onClick(DialogPreference.java:262)
E/AndroidRuntime( 3194):    at android.preference.Preference.performClick(Preference.java:811)
E/AndroidRuntime( 3194):    at android.preference.PreferenceScreen.onItemClick(PreferenceScreen.java:190)
E/AndroidRuntime( 3194):    at android.widget.AdapterView.performItemClick(AdapterView.java:284)
E/AndroidRuntime( 3194):    at android.widget.ListView.performItemClick(ListView.java:3246)
E/AndroidRuntime( 3194):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:1635)
E/AndroidRuntime( 3194):    at android.os.Handler.handleCallback(Handler.java:587)
E/AndroidRuntime( 3194):    at android.os.Handler.dispatchMessage(Handler.java:92)
E/AndroidRuntime( 3194):    at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime( 3194):    at android.app.ActivityThread.main(ActivityThread.java:4203)
E/AndroidRuntime( 3194):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime( 3194):    at java.lang.reflect.Method.invoke(Method.java:521)
E/AndroidRuntime( 3194):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
E/AndroidRuntime( 3194):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
E/AndroidRuntime( 3194):    at dalvik.system.NativeStart.main(Native Method)
I/Process (   86): Sending signal. PID: 3194 SIG: 3
I/dalvikvm( 3194): threadid=7: reacting to signal 3
I/dalvikvm( 3194): Wrote stack trace to '/data/anr/traces.txt'
I/Process ( 3194): Sending signal. PID: 3194 SIG: 9
I/ActivityManager(   86): Process tml.UI.main (pid 3194) has died.
I/WindowManager(   86): WIN DEATH: Window{4341fd00 tml.UI.main/tml.UI.main.MainActivity paused=false}
W/UsageStats(   86): Unexpected resume of com.android.launcher while already resumed in tml.UI.main
W/InputManagerService(   86): Got RemoteException sending setActive(false) notification to pid 3194 uid 10039