I have a PDC, Windows Server 2003, that has had a sporadic issue lately. It seems like it loses DNS which "fixes" itself when an admin (Domain or local) logs into the server. Then everything using DNS seems to be fine. (Exchange, intranet sites and so on). I have several errors in Event Viewer related to multiple identical login Event ID 11 (SQL and reporting servers), Master Browser election errors (Event ID 8003). I'm not sure why it suddenly returns to normal when a user logs into the server, but that seems to fix it (temporarily).