In your AD, just make sure the Computer accounts have at least read access to the User Accounts. It's easy to do. If you want to do it per users, just go in the properties of the user, select the "Security" tab, and add read access to "Domain Computers".
I had lots of trouble to find this. I hope this will be added to the wonderful doc by Joel.
(BTW: The registration system on the website doesn't seems to send me instructions nor password)
Jean-Sébastien Fortier
http://www.moofo.com