Authentication suddenly stops

Hi Everybody,

We have two servers with two network cards each. In each server one of the
network cards is configured for Network Load Balancing , port 80 only.

The NLB cards are connected to a VLAN with a subnet ranging from 10.xx.10.1
to 10.xx.10.127 and they have nothing on them except TCP/IP and NLB. They
have dns servers; lmhost and default gateway configured (10.xx.10.1).

The two other network cards are connected to another VLAN with a subnet
ranging from 10.xx.10.128 to 10.xx.10.255. The are configured with TCP/IP,
Client for Microsoft Networks and File sharing. They have no default gateway
nor dns servers.

After running this setup for a while (anything between 0 and 16 hours) users
not in ad are no longer authenticated. The event log shows Audit failures
for all these users with the event 537 and description An error occured
during logon. For example ...

--Event Type: Failure Audit
--Event Source: Security
--Event Category: Logon/Logoff
--Event ID: 537
--Date: 2005-03-02
--Time: 15:20:25
--User: NT AUTHORITY\SYSTEM
--Computer: xxx
--Description:
--Logon Failure:

Reason: An error occurred during logon
User Name: craas
Domain: yyyyyyyyyyyyy
Logon Type: 3
Logon Process: NtLmSsp
Authentication Package: NTLM
Workstation Name: xxxxxxxxxxxxxxxx
Status code: 0xC000005E
Substatus code: 0x0
Caller User Name: -
Caller Domain: -
Caller Logon ID: -
Caller Process ID: -
Transited Services: -
Source Network Address: 10.xx.xx.xx
Source Port: 0

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

In the event log (System) there are sporadic 5783 events (Netlogon). For
example ...

--Event Type: Error
--Event Source: NETLOGON
--Event Category: None
--Event ID: 5783
--Date: 2005-03-02
--Time: 13:00:26
--User: N/A
--Computer:zzz
--Description:

--The session setup to the Windows NT or Windows 2000 Domain Controller xxx
for the domain yyy is not responsive. The current RPC call from --Netlogon
on zzz to xxx has been cancelled.

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

These events occurs before or after the authentication stops working so they
do not seem relevant.



When trying to logon to the servers using the ipc$ share the following
message occurs

--System error 1311 has occurred.
--There are currently no logon servers available to service the logon
request.

Any help appreciated. If you need more info just let me know!

Thanks

Jonas