Can't activate

Hello

I get this error when activating CustomPress on my Wordpress installation.
Running: WP 3.0.4, BuddyPress1.2.7.

I get this error:
Fatal error: Call to undefined function is_network_admin() in /var/www/sportcoach.dk/public_html/wp-content/plugins/custompress/core/content-types.php on line 60

I'm not running Multisite.
Thanks for a quick reply.