The plugin works fine, but with one WordPress-Installation (3.2.1, Multiblog) I noticed a problem with the menu, caused by a conflict between two plugins.
In the WP-Backend the captcha-plugin inserts at the bottom of the menu (left column) the entry "BWS Plugins" and below "Captcha". Those entries were placed above (!) the menu-entry inserted by the plugin Contact Form 7 (http://contactform7.com/). I had to remove the Captcha-Plugin.