[Plugin: In Context Admin Notes] Error when activating

I get this error when activating. I deleted the plugin through my ftp and this message does not go away.

Fatal error: Call to undefined function wp_get_current_user() in /home/scadesi1/public_html/shopdemo/wp-includes/capabilities.php on line 1059

http://wordpress.org/extend/plugins/in-context-admin-notes/