We are running in a Windows 2003 Active Directory environment with 2 DNS
servers.  Occasionally we get DNS failures with little or no evidence in the
event viewer logs.  However recently I have noticed the event below which
occurred prior to the DNS failure:-

Event Type:    Warning
Event Source:    DNS
Event Category:    None
Event ID:    3000
Date:        6/22/2007
Time:        10:18:25 AM
User:        N/A
Computer:    ECSSWS2
Description:
The DNS server has encountered numerous run-time events. To determine the
initial cause of these run-time events, examine the DNS server event log
entries that precede this event. To prevent the DNS server from filling the
event log too quickly, subsequent events with Event IDs higher than 3000 will
be suppressed until events are no longer being generated at a high rate.

For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.