DNS server has encountered a critical error from the Active Directory

Hello -
I am trying to help troubleshoot some issues on a small office network with MS 2003 Small Business Server and  Win 2000 clients. We've had sporadic Internet / file sharing problems and then on Monday, one user lost his H:\ (home) mapped drive and then later his S:\ (shared ) netwqork drive letters which are mapped to the server. I'll paste in entries that seem related from the Event Viewer. Can anyone make heads or tails? I'm not a DNS or A.D. expert but it all seems to boil down to one or both of those is misconfigured. Here are the events:

=========================
Event Type:      Error
Event Source:      DNS
Event Category:      None
Event ID:      4015
Date:            11/15/2004
Time:            3:25:03 PM
User:            N/A
Computer:      [SERVER-NAME-HERE]
Description:
The DNS server has encountered a critical error from the Active Directory. Check that the Active Directory is functioning properly.

The extended error debug information (which may be empty) is "". The event data contains the error.

For more information, see

Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 51 00 00 00               Q...    


=================

Event Type:      Error
Event Source:      DNS
Event Category:      None
Event ID:      4004
Date:            11/15/2004
Time:            3:25:03 PM
User:            N/A
Computer:      [SERVER-NAME-HERE]
Description:
The DNS server was unable to complete directory service enumeration of zone _msdcs.[server].local.  This DNS server is configured

to use information obtained from Active Directory for this zone and is unable to load the zone without it.  Check that the Active

Directory is functioning properly and repeat enumeration of the zone. The extended error debug information (which may be empty) is

"". The event data contains the error.

For more information, see Help and Support Center at

http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 2a 23 00 00               *#..    


===========================

Event Type:      Error
Event Source:      DNS
Event Category:      None
Event ID:      4004
Date:            11/15/2004
Time:            3:25:03 PM
User:            N/A
Computer:      [SERVER-NAME-HERE]
Description:
The DNS server was unable to complete directory service enumeration of zone 1.168.192.in-addr.arpa.  This DNS server is

configured to use information obtained from Active Directory for this zone and is unable to load the zone without it.  Check that the

Active Directory is functioning properly and repeat enumeration of the zone. The extended error debug information (which may be

empty) is "". The event data contains the error.

For more information, see Help and Support Center at

http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 2a 23 00 00               *#..    


===========================

Event Type:      Error
Event Source:      DNS
Event Category:      None
Event ID:      4004
Date:            11/15/2004
Time:            3:25:03 PM
User:            N/A
Computer:      [SERVER-NAME-HERE]
Description:
The DNS server was unable to complete directory service enumeration of zone 7.168.192.in-addr.arpa.  This DNS server is

configured to use information obtained from Active Directory for this zone and is unable to load the zone without it.  Check that the

Active Directory is functioning properly and repeat enumeration of the zone. The extended error debug information (which may be

empty) is "". The event data contains the error.

For more information, see Help and Support Center at

http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 2a 23 00 00               *#..    


================================

Event Type:      Error
Event Source:      DNS
Event Category:      None
Event ID:      4004
Date:            11/15/2004
Time:            3:25:03 PM
User:            N/A
Computer:      [SERVER-NAME-HERE]
Description:
The DNS server was unable to complete directory service enumeration of zone [SERVER].local.  This DNS server is configured to

use information obtained from Active Directory for this zone and is unable to load the zone without it.  Check that the Active

Directory is functioning properly and repeat enumeration of the zone. The extended error debug information (which may be empty) is

"". The event data contains the error.

For more information, see Help and Support Center at

http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 2a 23 00 00               *#..    

=======================

Event Type:      Warning
Event Source:      NTDS ISAM
Event Category:      Performance
Event ID:      507
Date:            11/15/2004
Time:            10:58:08 PM
User:            N/A
Computer:      [SERVER-NAME-HERE]
Description:
NTDS (556) NTDSA: A request to read from the file "C:\WINDOWS\NTDS\ntds.dit" at offset 9969664 (0x0000000000982000) for

8192 (0x00002000) bytes succeeded, but took an abnormally long time (104 seconds) to be serviced by the OS. This problem is

likely due to faulty hardware. Please contact your hardware vendor for further assistance diagnosing the problem.

For more

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