Here is a good tip for Mac OS X computers trying to connect to a local Windows2003 Server that has ActiveDirectory running.
First go to Microsoft’s site and download the User Authentication Module, otherwise known as UAM for short. Install this for Mac OS X, and then you will need to make one change on the Windows2003 Server.
You will need to login as administrator and go to Administrative Tools and open Domain Controller Security Settings. From here go to Local Policies then Security Options. Scroll down to find the entry:
Microsoft network server: Digitally sign communications (always).
Set this to Disabled, so it looks like this. Then from a cmd prompt type: gpupdate and once that completes, reboot the server.
From the Mac client station, use the Go menu and choose Network. You should now be able to login via UAM with a domain account and mount the shares from Windows2003 Server on your Mac OS X desktop.
Apparantly the Connect To Server option defaults to Apple Authentication and will still not work with 2003 Server.