Fatal error: Class '*_Model_Resource_Setup' not found in includes\src\Mage_Core_Model_Resource_Setup.php on line 234

http://stackoverflow.com/questions/9392111/mage-checkout-model-mysql4-setup-not-found-on-magento

It looks like you are running Magento in 'compiled modus', but something went wrong. Have a look at /home/xxxxx/public_html/xxxxxx/includes/config.php. There are two define() statements in there. Comment them out and try again.