Malformed URL when submitting form

When attempting to save options on the plugin’s config page, I get this error: “You do not have sufficient permissions to access this page”

The reason I’m getting this error is because it sends me to

http://firefi.re/testbed/bitcoinmagazine/wp-admin/admin.php/testbed/bitcoinmagazine/wp-admin/admin.php?page=wordpress-related-posts?page=wordpress-related-posts

instead of

http://firefi.re/testbed/bitcoinmagazine/wp-admin/admin.php?page=wordpress-related-posts

I’m not sure why it’s adding all the extra bits, but perhaps due to using Nginx? Any assistance with this would be appreciated.

http://wordpress.org/extend/plugins/wordpress-23-related-posts-plugin/