I got this error message on the error log

[Tue Jan 27 08:38:21.823571 2015] [fcgid:warn] [pid 31511:tid 139962559170304] [client 50.128.237.1:64314] mod_fcgid: stderr: PHP Fatal error: Access to undeclared static property: next_level_cache_wpdb::$CACHE_WRITE_WHITELIST in /home/wbpl/public_html/wp-content/db.php on line 478, referer: http://example.com/wp-admin/post-new.php

I have been having database issues with my hosting company (godaddy) and they made me notice this error message as a factor, which I doubt is the cause but you never know.

https://wordpress.org/plugins/next-level-cache/