[Samba] Windows 2003 and Samba 3.0.x

[Ronald Roche]

My Windows 2003 machines can get to shares on my older Samba servers 
(2.2.8a), however on newer versions of Samba (3.0.2), I get the following 
error message:

\\servername is not accessible.  You might not have permission to use this 
network resource.  Contact the administrator of this server to find out if 
you have access permissions.  The request is not supported.

These same shares are accessible via other windows platforms (2000, XP).

Is there a version of Samba I should be running?
Is there a change I can make to my Windows 2003 machines to fix this?

Thanks in advance,

Ron