Outlook 2000 keeps asking password when opening OST files

[Mel]

Hello,

When opening an ost file on a laptop we keep getting the prompt box to enter
the password.
If we enter the Exchange Enterprise password it works. If we start outlook
with /s it also works perfect.
But when we enter the users credentials, the client fails to open.

We have following situation:
Exchange 5.5
Outlook 2000 clients
NT authentication is on

We already tried following solutions:
Article ID: 321652 (microsoft)
We removed the outlook profile and ost file
We removed the NT profile.
Reinstalled outlook.

And none of these solutions seems to work.

Has somebody some ideas?

Thanks in advance,