I just tried to activate the plugin on WordPress 2.8.4 and received the following error:

Mywebsite/wp-content/plugins/wp_pageflip/functions.php) [function.main]: failed to open stream: No such file or directory in /homepages/19/d******/htdocs/Mywebsite/wp-content/plugins/wp-pageflip/wp_pageflip.php on line 30