Query Cache Not Working With Cglobalstatecachedependency

After I update my manufacturer table, I set the global state as follows:

    Yii::app()->setGlobalState('manufacturer_updated', new DateTime());

But the cache listing of getAllManufacturers call from dropdown box is not getting refreshed:

    <?php echo $form->dropDownList($model,'manufacturer_id', CHtml::listData(Manufacturer::model()->getAllManufacturers(), 'id', 'name'), array('prompt'=>'Select Manufacturer')); ?>

Function in my model called by the dropdownbox:

    public function getAllManufacturers()


		$sql = 'SELECT id, name FROM manufacturer WHERE store_id =:store_id ORDER BY name';

		$cmd = Yii::app()->db->cache(72000, new CGlobalStateCacheDependency('manufacturer_updated'))->createCommand($sql); //20 hours cache

		$cmd->bindValue(':store_id', Yii::app()->session["current_store_id"], PDO::PARAM_INT);

		return $cmd->queryAll();


Actually, 2-3 times it worked in the beginning. After that, the cache is never getting refreshed. However, changing the expiry time to 0 causes it to get refreshed. But when I set back the expiry value to its original, the cache strangely brings back its stale data.

Why is this query cache still keeping its stale data?

It is working well now after restarting my memcache server. I think when we make any code changes on this, we have to restart the cache server. Can anyone please comment on this?