$_GET conflict between Magic Members and WordPress SEO by Yoast

I was having a problem with the logout shortcode where I was unable to logout. Disabling Magic Members solved the problem. I contacted Magic Members and they said that the problem is WordPress SEO and the $_GET variable. They said

“We debugged the site environment and found that GET variables were killed by some plugin, we tested all active plugins and found “WordPress SEO” responsible…
Since we can not fix “WordPress SEO” problem either you can contact the plugin author or use different Plugin.”

and

“The predefined $_GET variable is used to collect values in a form with method=”get”. We have used $GET variable to print values.It does not return any value when WordPress SEO plugin was installed.”

I don’t know enough to know which plugin is to blame. I am hoping that by posting this here, this will lead to the appropriate plugin getting improved.

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