Category grid doesn't show categories on homepage

Question

I have multiple stores in my Magento. For each store I have created a home page in CMS > Pages > Manage pages. At the design tab I use this layout update XML code:

<reference name="content">
<block type="catalog/product_new" name="home-categories" template="custom/category_grid.phtml" after="-"/>

<!--
<block type="catalog/product_list" name="product_list" template="catalog/product/list.phtml">
<action method="setColumnCount"><columns>4</columns></action>
</block>
-->
</reference>

The result of including this code in the layout update XML textarea is that each category will be displayed at the homepage. See screenshots below:

Here the categories are working: (the <ul> tag is included in the html)

Here the categories aren't working: (the <ul> tag is not included in the html)

The problem is that one store doesn't show the categories in the grid. I think that the solution to this problem lays somewhere else but I don't know where to look. Where can I look?

Update

The code of function getSelectSQL in "lib\Varien\Data\Collection\Db.php"

function getSelectSql($stringMode = false)
    {
        if ($stringMode) {
            return $this->_select->__toString();
        }
        return $this->_select;
    }

Answer 1

You are using block type catalog/product_new, but you are outputting with template category_grid. According to your question it sounds like you are trying output category collection. But in your block definition in section type you are trying to get PRODUCT COLLECTION.

Please clarify your goal. What do you need to output? Categories or products?

And i'd like to draw your attention on method _getProductCollection(). It has following rows:

        ->addAttributeToFilter('news_from_date', array('or'=> array(
            0 => array('date' => true, 'to' => $todayEndOfDayDate),
            1 => array('is' => new Zend_Db_Expr('null')))
        ), 'left')
        ->addAttributeToFilter('news_to_date', array('or'=> array(
            0 => array('date' => true, 'from' => $todayStartOfDayDate),
            1 => array('is' => new Zend_Db_Expr('null')))
        ), 'left')

If you have no products, created during this period - you'll get empty result.