This isn't strictly to do with GP, but can affect it and a lot of other services, so I figured that I'd try to help other by sharing my pain. Scenario: Win 2003 Domain with two DC's. One Win 2003 and the other a new Win 2008, installed about a month ago. Yesterday the 2008 box began getting tons of errors. DCHP, DNS, replication, Group Policy, WINS, basically anything that involved the 2008 DC trying to communicate with the 2003 DC. After wasting an entire day chasing generic or obtuse error messages, I spent a few hours removing services from the 2008 machine, demoting it, removing it from the domain, rejoining the domain, re-promoting it, and adding services back. Then the errors started coming back again. Thankfully I hit paydirt on one of them. Group Policy 1006. This led me to http://forums.technet.microsoft.com/en-US/winserverDS/thread/3fdc100f-16cb-4d4d-b1ca-4ce00bc7bbcc/ , which led to http://support.microsoft.com//kb/939820 and a hotfix. The issue affects more than is listed in the article. It also took weeks to manifest itself in my environment. Just something to look out for if you are adding a 2008 DC to a domain with existing 2003 DCs. Scott Klassen