Can not perform this action after onSaveInstanceState (onClick preference)

Here is my PreferenceActivity (Inner class of my Main Activity)

public static class TestSettings extends PreferenceActivity implements Preference.OnPreferenceClickListener{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.pref);
        getPreferenceManager().findPreference("key").setOnPreferenceClickListener(this);

    }

Here is my onPreferenceClick:

@Override
public boolean onPreferenceClick(Preference preference) {
    FragmentClass fc = new FragmentClass();
    fc.show(fm, "TAG");
    return false;
}

And here is my FragmentClass ( TimePicker dialog ):

public class FragmentClass extends DialogFragment implements TimePickerDialog.OnTimeSetListener {

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        return new TimePickerDialog(getActivity(), this, 15, 00, false);
    }


    @Override
    public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
        Log.i("APP", "hour: "+hourOfDay+", min: "+minute);
    }
}

PROBLEM:

When I click on preference (defined in XML ), and when I handle onClick (I'm showing TimePickerDialog onClick) I got following exception:

  03-21 10:06:41.325: E/AndroidRuntime(11003): FATAL EXCEPTION: main
03-21 10:06:41.325: E/AndroidRuntime(11003): java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
03-21 10:06:41.325: E/AndroidRuntime(11003):    at android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:1327)
03-21 10:06:41.325: E/AndroidRuntime(11003):    at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1338)
03-21 10:06:41.325: E/AndroidRuntime(11003):    at android.suppo