Certain accounts unable to a log in to OWA

[Seryth]

Hello everyone, just a quick question. It appears that we are having an issue where certain user accounts are unable to access OWA, they can log in to the domain perfect and access Exchange through Outlook, but anytime they try to log in to OWA it gives the error message:

>> "You could not be logged on to Outlook Web Access. Make sure your user name and password are correct, and then try again." <<

Obviously the domain, username and password are correct, this only seems to be affecting certain accounts the majority of user accounts have no problems whatsoever, it appears to be accounts created recently. Any ideas?

Running Exchange 2003 (upgraded from 2000) on a Windows 2000 domain also providing OMA.

 

[xmsre]

What is unique about those specific user accounts? Is their primary smtp address the same as everyone else? How long and what kind of characters are in the user name? What is the client OS? Does it matter which workstation the user attempts to log on from?