Magento issue: Cleared the system cache and now the product category pages display a fatal PHP error. The backend dashboard and the frontend categories, home, and checkout system appear to work fine, but product pages will not display. Product view page throws the following error:
"PHP Fatal error: Call to a member function addToChildGroup() on a non-object in E:\inetpub\vhosts\[login to view URL]\httpdocs\shop\app\code\core\Mage\Core\Block\[login to view URL] on line 759"
Tried fixing the permission settings for var, .htaccess, etc, and others, but couldn't get it to work.
The ideal solution would entail making the product pages display and setting the permissions to entail the most security while ensuring functionality.