Question : EBS 2008 Server Problem

I have a strange problem with my Active Directory Users and Computers under Microsoft EBS 2008  [Essential Business Server]. Every 6 - 8 hours, I'm receiving this error message from all the clients machines:
'Your account is configured to prevent you from using this computer. Please try another computer.'

By checking the Active Directory Users and Computers, I will find that under the User-->Properties..>Account-->Log On To, that This user can log on to changed from 'All Computers' to 'The Following Computers' and there is a list of computers shown [mainly servers].

I have to manually check each account and change it back to: 'All Computers' and everything will work fine again. After 6-8 hours again the same problem happened and the users can't access their machines again.

It's not convenient at all to have such a practice, every 6-8 hours this problem automatically happened.

Can anyone advise me what to do with this Essential Business Server 2008 Active Directory problem? All the clients are running on  Windows Vista Business Edition.

Best Regards

Answer : EBS 2008 Server Problem

This is accually an annoying issue, but the solution is VERY SIMPLE!...

Open up EBS Admin Console on Management Server... Select Licencing and make sure that user has a licence. Without a license it goes into the user properties in AD Users Computers and Restricts the logon as to only the servers.

As other users pointed out... its the CALS, just thought i'd elaborate on the fix.