I suppose it only could be related to the wrong database request which this script generates in your installation. Did you made any sort of customizations to your users table? You must make sure all fields in the users table are present as they are present in default package.
Default mySQL request this script makes, is like the following:
SELECT user_id, username, user_email, user_icq, user_website, user_from, user_viewemail, user_regdate, num_posts FROM minibbtable_users WHERE activity='1' order by (username=''), username ASC, user_regdate DESC limit 0,30
Make sure your users table has all these fields present. If you have a way to execute this request manually in your mySQL client (change minibbtable_users
if you have a different table name), it would be worth of trying - in this case, the client would give you an exact mySQL error.