Supporter instant crash

I installed supporter. All I get is an error message.

Fatal error: Call to undefined function is_site_admin() in /home2/bizficom/public_html/financemark/wp-content/mu-plugins/supporter-framework.php on line 211

I'm using wp3.0 - no wpmu install because it is supposedly deprecated.

http://codex.wordpress.org/Installing_WPMU