Magento

Once a day I get the following error message:

Warning: include_once(Mage/Core/functions.php) [function.include-once]: failed to open stream: No such file or directory in /var/www/vhosts/whitefirebrands.com/httpdocs/magento/app/Mage.php on line 49

Fatal error: Class ‘Varien_Autoload’ not found in /var/www/vhosts/whitefirebrands.com/httpdocs/magento/app/Mage.php on line 53

The error happens almost every afternoon. Every morning, the site seems to work fine. Then, all of the sudden, the error comes up for a while. Several hours later without changing anything, all of the sudden, the error does not show and the site works as it should.

Any ideas as to how to fix this permanently?

I’ve noticed that once I get the error message, in some instances if I simply refresh the page, the error message goes away and the page loads and functions as it should.