oscarv514 on "[Plugin: WooCommerce - excelling eCommerce] fatal error message in my page"

hi i download woocommerce plugin in my wordpress and im using a wordpress theme which i already fix the page layout.
The problem im having is everytime i go to my webpage i get this error :Fatal error: Class 'WC_Product_Simple' not found in \html\wp-content\plugins\woocommerce\classes\class-wc-product-factory.php on line 62
i have to refresh the page every time and the error message desappears, please i need you help ,i have download this plugin 3 days ago i will like to keep this plugin.

http://wordpress.org/extend/plugins/woocommerce/