Prior versions immediately took you to the post editing window upon duplication which did two important thing.
1: let you know that a post has been duplicated
2: allowed you to edit the duplicated post BEFORE publishing it to the site.
The current version of the plugin with wp 3.2.1 simply reloads the posts page without any notification that a post has been duplicated. Meanwhile it actually does duplicate the post verbatim with out nay notification of doing so.
This causes problems because if you click the "duplicate" button a couple times in effort to try to get it to work, it silently not only does duplicate the post, but immediately publishes them to your site without any confirmation.