can't activate Ning-Buddypress-Importer plugin

Hello, I am trying to install the Ning-Buddypress-Importer plugin and I get a fatal error when I activate it.
I am using wordpress 2.9.2, buddypress 1.2.3 and have deactivated all other plugins so only buddypress is activated and it still does not work.

The actual error is Fatal error: Call to undefined function is_multisite() in /home/naturalp/public_html/goder/wp-content/plugins/ning-buddypress-importer/includes/ning-buddypress-importer.php on line 80

any insight to this?

Thanks in advance!