Fatal Error lib/class_bau_installer.php

I'm transferring all my old mu-plugins into plugins (finally!!) and when I activate Blog & User Creator I'm getting the following message:

Warning: require_once(/home/allthing/public_html/wp-content/plugins/blogs-and-users/lib/class_bau_installer.php) [function.require-once]: failed to open stream: No such file or directory in /home/allthing/public_html/wp-content/plugins/blogs-and-users/blogs-and-users.php on line 73

I'm running WP 3.2.1 on allthingsquilting.com.au