             {
                 data = iterator.current;
                 ch = 0;
-                n = columns.length;
+                n = _columns.length;
                 for (j = 0; j < n; j++)
                 {
-                    c = columns[j];
+                    c = _columns[j];
 
                     if (!c.visible)
                         continue;

        else if (shiftKey && code == Keyboard.PAGE_DOWN)
        {
            // We don't want to exceed the max scroll value or the last column's index
            maxPosition = Math.min(maxHorizontalScrollPosition, columns.length-1);
            newHorizontalScrollPosition = Math.min(
                horizontalScrollPosition + (visibleColumns.length - lockedColumnCount)
                , maxPosition);

        if (isKeyPressed && headerIndex != -1)
        {
            isKeyPressed = false;
            selectedHeaderInfo = getHeaderInfo(_columns[headerIndex]);
            selectColumnHeader(headerIndex);
        }
    }
