I am getting similar problem started today:
Warning: preg_match() [function.preg-match]: Unknown modifier ‘2’ in /home4/lunsford/public_html/cincyshopper.com/wp-content/plugins/wordpress-seo/admin/class-metabox.php on line 1690
Warning: preg_match() [function.preg-match]: Unknown modifier ‘2’ in /home4/lunsford/public_html/cincyshopper.com/wp-content/plugins/wordpress-seo/admin/class-metabox.php on line 1690
Warning: Cannot modify header information – headers already sent by (output started at /home4/lunsford/public_html/cincyshopper.com/wp-content/plugins/wordpress-seo/admin/class-metabox.php:1690) in /home4/lunsford/public_html/cincyshopper.com/wp-includes/pluggable.php on line 876
