photosite.de on "[Plugin: NextGEN-ImageFlow] Setting is causing a fatal error"

Calling the setting after activation gives the following error

Fatal error: Class 'CheckPlugin' not found in /mnt/webg/XXXXX/htdocs/blog/wp-content/plugins/nextgen-imageflow/admin/admin.php on line 47

http://wordpress.org/extend/plugins/nextgen-imageflow/