Fatal error: Out of memory (allocated 6291456) (tried to allocate 7680 bytes)
This is usually caused by Wordpress, Drupal or other ridiculously inefficient CMS' out there, as a temporary fix you can increase PHP's memory limit but it's best to find the actual culprit, by disabling add-ons and other scripts etc...........
PDOException: SQLSTATE[42000] [1044] Access denied for user 'db_user'@'localhost' to database 'dbname' in lock_may_be_available() (line
167 of /home/user/public_html/includes/lock.inc).
The username and password were correct but some reason CPanel added the user with no permissions! Edit the user's permissions to include "All" from Cpanel or MySQL and that is the solution.........