"SQLiteCantOpenDatabaseException: unable to open database file (code 14)"

I'm getting an error stating: "SQLiteCantOpenDatabaseException: unable to open database file (code 14)" on the line: if (cursor != null && cursor.moveToFirst()) {

and on

data = dbHelper.getTblQuoteNotify("tblQuoteNotify", nCounter);

I have <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> which seems to be the most common resolution to this issue from my research - can anyone else take a look at the code below and let me know what I may have done wrong in this instance?

Source:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    doTimerTask();
    setContentView(R.layout.activity_main);
    data_textview = (TextView) findViewById(R.id.data);
    timer = (TextView)findViewById(R.id.timer);
    dbHelper = new DBHelper(this);
    try {
        dbHelper.CopyDataBaseFromAsset();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    dbHelper.openDataBase();
    data = new Data();
}

 public void doTimerTask(){

        mTimerTask = new TimerTask() {
                public void run() {
                        handler.post(new Runnable() {
                                public void run() {
                                    nCounter++;
                                        // update TextView
                                    timer.setText("Notify: " + nCounter);

                                    data = dbHelper.getTblQuoteNotify("tblQuoteNotify", nCounter);
                                    if (data != null) {
                                        data_textview.setText(data.tblQuoteNotify);                                     
                                    }