I am having the same issue at http://www.accucode.com/wordpress
The website itself from the user end is fine, but trying to hit the backend, I get:
W3 Total Cache Error: some files appear to be missing or out of place. Please re-install plugin or remove /var/www/vhosts/accucode.com/httpdocs/wordpress/wp-content/db.php.
This error popped up after uninstalling W3 Total Cache. I have tried putting the w3tc folder back into /plugins to no avail. I have tried deleting db.php, and the error message does not change. I have also tried deleting advanced-cache.php and w3-total-cache-config.php.
I have a working backup of the site and database I can revert to, but I would prefer not to since there have been significant changes since the last backup.