samba - Jun 2004 - Problem with authenticating a computer to a samba share

Hi,

I have a Win2k Server Active Directory Domain Controller, and an 
Exchange server running on the same machine. I want to use NTBACKUP to 
back up the mailboxes to a Samba machine running as ADC slave. This 
doesn't work, and I get the message

	Username DOMAIN\MACHINE$ is invalid on this system

in the Samba logs.

How can I make MACHINE known to Samba? Since MACHINE is the domain 
controller, I can't add it to the ADC host list, and it's the one that 
supplies the passwords...

Anyone seen/done this before?

Thanks a lot in advance,
Bj?rn