Putting an “*” in username field brings up a list of all AD user accounts!!!!

We have been using the golden triangle for about three years now. Just recently we had a security issue where users logged into an account they should not have been in. While observing the user with ARD we noticed he put an asterisk(*) in the Usename box, hit login and was quite surprised when a complete list of AD users appeared. We have tried speaking with reps from Apple, other companies and several mac-windows forums. I'm hoping someone can tell me there is a fix for this. The result lead to an arrest of that user. My superiors are not taking this lightly. Comments have even be made to let Macs be Macs and remove the AD plug-in. Any help or direction would be greatly appreciated. Thanks Bob