Notice: wpdb::escape is deprecated since version 3.6! Use wpdb::prepare() or esc_sql() instead. in /nfs/c01/h04/mnt/38315/domains/joao.pt/html/wp-includes/functions.php on line 2905
WordPress often is not really accurate with giving your information. You can change that: Set error_reporting( -1 ); and define( 'WP_DEBUG', true );. More info in that Gist. This will avoid the white screen of death.
If you got XDebug installed, every error normally comes with a backtrace of what happened. If you even got an IDE like PHPStorm, you’ll be able to remote debug your pages and see your errors very accurate and fast.
If you ain’t got any of that, your best bet is deactivating all plugins, switching back to the default theme and then activate one after the other step by step to see when the error occurs. If you found the plugin or theme responsible, do a cross file search for escape. Then change it according to the error message.