By default, Windows 2003 Server domain controllers have “Microsoft network server: Digitally sign communications (always)” set to “Enabled” by default. This is likely causing the Macs to fail to authenticate with the “error = -5000” when trying to connect via CIFS or SMB (samba)
To change this on a given domain controller, go to “Start” ->”Administrative Tools” -> “Domain Controller Security Policy” (not Domain Policy) and look for “Security Settings” -> “Local Policies” -> “Security Options” -> “Microsoft network server: Digitally sign communications (always)”. It should show “Enabled” by default. Double-click on it and set to “Disabled”.
Then close the app and click on start | Run – enter the command ‘gpudate’ to refresh group policy and hit enter.
You should now be able to use the “Go” > “Connect to Server” command in Finder to map to a share as shown below: