Outlook keeps requesting password


I am running Exchange 2003 for a mail server, and Windows Small Business Server 2003 as my NOS.

When users attempt to open Outlook and gain access to their mailbox, the system is prompting them for a username/password. Even when the correct credentials are entered, the box just prompts them again, and again...

This has started to happen on Friday morning and has reoccurred everyday since. It seems to affect about 5 people in a group of 12.

All other network services are up and running fine and only Outlook is problematic. There has been no other changes to the network.

A work-around is to get the user to restart their machine though it can take several attempts for the prompts to stop appearing.

I have no clue where I should go from here... any help is greatly appreciated.

Many thanks
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To solve this please follow the steps,

Open MS Outlook-->Tools-->Otions-->Mail Setup-->Email Accounts-->Email-->Change--> More Settings-->Security--> Un tick "Always Prompt for logon credentials"

Close and open the outlook again.
Try NTLM authentication:
In the Mail dialog box, click your Outlook profile, and then click Properties.
Click E-mail Accounts, and then click Change.
In the Change E-mail Account dialog box, click More Settings.
In the Microsoft Exchange dialog box, click the Security tab.
In the Logon network security list, click Password Authentication (NTLM), and then click OK.
Click Next, click Finish, and then click Close two times.

If that works then have a read of this: http://support.microsoft.com/kb/927612
Have you checked all the servers that Outlook is connected to (with outlook /rpcdiag) to ensure that they are displaying the correct time since the DST time change over the weekend?
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granite03Author Commented:
moorthipvm: The "Always prompt for logon credentials" was always unticked.

MegaNuk3: The mailboxes are all set to use Password Authentication (NTLM) already.

I just opened Outlook using outlook /rpcdiag and the first time, it would not accept the password. I pressed cancel and, reattempted and this time it worked? Clearly something isn't working as it should be.
keep the rpcdiag box open and see which servers it is hitting for "directory" and see if that name changes with each attempt.
granite03Author Commented:
I don't have currently access to any of the machines, and if it could cause them to restart their machines' I'd would rather avoid the downtime until the problem reoccurs.

From  memory of the first time though, it was attempting to hit the exchange server and failing.
If the problem is still occuring then run the Exchange Best Practice Analyser SBS 2003 Version:

See if it highlights anything like Checksum offloading that can affect network connectivity to the server.
granite03Author Commented:
I managed to figure it out. Our old DC which is now our TS had the incorrect time (was a few minutes behind) and that was what was causing the issue.

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thanks for the update, I'll make a note of the fact that time can cause this issue
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