[Plugin: WP e-Commerce] Simple-Facebook-Connect – Fatal error: Call to a member function get()..line

I use Simple-Facebook-Connect and wp-e-commerce not work!

In the store page I get a blank page with the widget facebook publisher showing this error code:

Fatal error: Call to a member function get() on a non-object in /home/…./…./wp-includes/query.php on line 27

any idea?

Thanks

http://wordpress.org/extend/plugins/wp-e-commerce/