On the Windows 2000/2003 Server
In order for a Mac client to authenticate with Active Directory, Services for Macintosh must be installed on the Windows Server. These components can be added by using Add/Remove Programs, choosing Add/Remove Windows Components, scrolling to ‘Other Network File and Print Services’, and then selecting ‘File Services for Macintosh’ (likely you will also want ‘Print Services for Macintosh’).
If you are trying to access a file share located on a Windows Server 2003 Domain Controller, the Default Domain Controllers security will prevent Mac clients from connecting. In order to allow the Mac client to connect, the Default Domain Controllers policy must be modified to “weaken” the network communications. If you can move the file share for the Mac clients off of a Domain Controller, to s Windows 2003 member server you should not have this issue, unless the member server has been configured to use a policy with the same setting as described below. This is because the security policy is set to always encrypt network connections. Word has it, that is was not an issue in Samba 3, but it is for OS 10.
If you choose to change this policy for the Domain Controllers, open the policy and go to:
Administrative Tools/Domain Controller Security Settings.
Within the Policy Editor go to:
Local Policies/Security Options
Find the policy entry, ‘Microsoft network server: Digitally sign communications (always)’ and change it to ‘Disabled’.
You need to run ‘gpupdate’ to reload the security policy.
On the Macintosh Client
If you are trying to authenticate to a Windows 2003 Server Active Directory, the Macintosh client will need to have the Microsoft User Authentication Module (UAM) installed. This is because the Windows Server 2003 Services for Mac only permits Microsoft Authentication by default. You can download the UAM athttp://www.microsoft.com/mac/otherproducts/otherproducts.aspx?pid=windows2000sfm
If you are running a Mac OS version prior to 10.4.3, there is a known issue that prevents Active Directory users from accessing certain Kerberized services on a Windows 2003 server. There is a patch 10.4.x clients which should resolve the problem and can be found here http://docs.info.apple.com/article.html?artnum=301722.
More information on connecting Mac clients to Windows 2003 can be found in Microsoft KB Article 834498 - Macintosh client cannot connect to Services for Mac on Windows Server 2003.