infolotnicze on "[Plugin: WordPress SEO by Yoast] Php error"

Plugin gives an error from time to time:
[02-Jul-2013 09:19:44] PHP Warning: preg_match() [function.preg-match]: Unknown modifier 'P' in /xxxxxxx/wp-content/plugins/wordpress-seo/admin/class-metabox.php on line 1690

http://wordpress.org/extend/plugins/wordpress-seo/