I see that it is a horror error commonly encountered by those who use pluginthe WordPress , All-in-one-SEO-pack.

Catchable fatal error: Object of class WP_Error could not be converted to string in /home/user/public_html/wp-content/plugins/all-in-one-seo- pack/aioseop.class.php on line 285.

The error appears in Custom pages which are created outside the folder/WP-account/Themes/theme (gender, this), and can be eliminated with the deletion of the function:

<?php get_header(); ?>

... from the template of the page.
It is a little extreme sports, because an import of style.css, but for those who have extreme sports ... it's a method.
If you have another solution to the problem ... the comments are open. :-)

Another error that appears in Custom Pages due to SEO plugin, and also in aioseop.class.php, but on another line, it is:

Warning: error_log(/home/panamea/public_html/wp-content/plugins/all-in-one-seo-pack/all_in_one_seo_pack.log) [function.error-log]: failed to open stream: Permission denied in /home/panamea/public_html/wp-content/plugins/all-in-one-seo- pack/aioseop.class.php on line 976

This is solved simpler. The option is deactivated “Log important events” from the options of the plugin All in One SEO.