How to fix [object XMLHttpRequest] Error on Prestashop


TECHNICAL ERROR: unable to add the product.
Error thrown: [object XMLHttpRequest]
Text status: error
Fresh install nothing done to PrestaShop, get the error when I try to add an item to the cart?

Prestashop 1.4.7
MAMP 2.0.3
PHP 5.3.6 -> Cache = "none"
MySQL 5.5.9


in the file classes/FrontController.php, please replace following line :
'content_dir' => $protocol_content.Tools::getServerName()._PS_BASE_URI_,
To the following :
'content_dir' => $protocol_content.Tools::getHttpHost()._PS_BASE_URI_,