I loved this plugin, so I needed it in spanish. I uploaded it to Dropbox:
I found there is one non-translatable string. In the Users Screen, at the top you have the list of filters, and "Unapprove" is not in the pot file, yet it is set to find a translation from wp-approve-user.php. I tried to add it to the pot/po/mo using poedit, to not avail. You'll see it in the last line of .pot and .po files. Fix it as you need.