Android-Fehler: können diese operation Nicht ausführen, da die Verbindung pool geschlossen wurde

Habe ich danach gesucht, StackOverflow und das web nach einer Antwort auf diese Frage, aber ich konnte keine Antwort finden. Wenn ich meine Anwendung auf Lebkuchen, es läuft wunderbar. Aber wenn ich es auf 4.2.2, bekomme ich diesen Fehler: java.lang.IllegalStateException Cannot perform this operation because the connection pool has been closed
Ich habe eine SherlockFragmentActivity enthält zwei Fragmente.

Fragment 1:

public final class TodoFragment extends SherlockListFragment {
NotesDbAdapter db;

private static final int DELETE_ID = Menu.FIRST + 1;

public static TodoFragment newInstance(String s) {
    TodoFragment fragment = new TodoFragment();

    return fragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    db = new NotesDbAdapter(getActivity());

}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    if (container == null) {
        return null;
    }

    return ll;

}

Fragment 2:

public final class NotesFragment extends SherlockListFragment {
NotesDbAdapter db;
private static final int ACTIVITY_EDIT = 1;

private static final int DELETE_ID = Menu.FIRST + 1;

public static NotesFragment newInstance(String content) {
    NotesFragment fragment = new NotesFragment();

    return fragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    db = new NotesDbAdapter(getActivity());

    db.open();
    if (db.fetchAllNotes().getCount() == 0) {
        doWelcomeMessage();
    }
    db.close();

}

private void doWelcomeMessage() {
    //Show welcome dialog
    startActivity(new Intent(getActivity(), NotesWelcome.class));

}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    if (container == null) {
        return null;
    }

    db = new NotesDbAdapter(getActivity());

    db.open();
    if (db.fetchAllNotes().getCount() == 0) {
        doWelcomeMessage();
    }
    db.close();


    return ll;

}

SherlockFragmentActivity:

public class NotesFragmentActivity extends SherlockFragmentActivity {

ViewPager mViewPager;
TabsAdapter mTabsAdapter;
TextView tabCenter;
TextView tabText;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    mViewPager = new ViewPager(this);
    mViewPager.setId(R.id.pager);

    setContentView(mViewPager);
    ActionBar bar = getSupportActionBar();
    bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    mTabsAdapter = new TabsAdapter(this, mViewPager);

    mTabsAdapter.addTab(bar.newTab().setText("Notes"), NotesFragment.class,
            null);
    mTabsAdapter.addTab(bar.newTab().setText("Todo List"),
            TodoFragment.class, null);

}

public static class TabsAdapter extends FragmentPagerAdapter implements
        ActionBar.TabListener, ViewPager.OnPageChangeListener {
    private final Context mContext;
    private final ActionBar mActionBar;
    private final ViewPager mViewPager;
    private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();

    static final class TabInfo {
        private final Class<?> clss;
        private final Bundle args;

        TabInfo(Class<?> _class, Bundle _args) {
            clss = _class;
            args = _args;
        }
    }

    public TabsAdapter(SherlockFragmentActivity activity, ViewPager pager) {
        super(activity.getSupportFragmentManager());
        mContext = activity;
        mActionBar = activity.getSupportActionBar();
        mViewPager = pager;
        mViewPager.setAdapter(this);
        mViewPager.setOnPageChangeListener(this);
    }

    public void addTab(ActionBar.Tab tab, Class<?> clss, Bundle args) {
        TabInfo info = new TabInfo(clss, args);
        tab.setTag(info);
        tab.setTabListener(this);
        mTabs.add(info);
        mActionBar.addTab(tab);
        notifyDataSetChanged();
    }

    @Override
    public int getCount() {
        return mTabs.size();
    }

    @Override
    public Fragment getItem(int position) {
        TabInfo info = mTabs.get(position);
        return Fragment.instantiate(mContext, info.clss.getName(),
                info.args);
    }

    public void onPageScrolled(int position, float positionOffset,
            int positionOffsetPixels) {
    }

    public void onPageSelected(int position) {
        mActionBar.setSelectedNavigationItem(position);
    }

    public void onPageScrollStateChanged(int state) {
    }

    public void onTabSelected(Tab tab, FragmentTransaction ft) {
        Object tag = tab.getTag();
        for (int i = 0; i < mTabs.size(); i++) {
            if (mTabs.get(i) == tag) {
                mViewPager.setCurrentItem(i);
            }
        }
    }

    public void onTabUnselected(Tab tab, FragmentTransaction ft) {
    }

    public void onTabReselected(Tab tab, FragmentTransaction ft) {
    }
}
}

Ich Hänge schon länger an diesem für STUNDEN (keine Witze), und würde wirklich zu schätzen jede Hilfe. Nochmals vielen Dank.