Mac OS X operates on a Windows network OK, its visible in Entire Network | Microsoft Network and it can access Windows hosted resources. But...
The Mac appears in "Workgroup" not in the Windows Domain: even though it is being handed all its information via DHCP, and that service includes DNS, Default Gateway, etc.
The secret to the SMB networking in Mac OS X is held in the Directory Access utility. Click the Services tab, make sure the SMB service is check-marked and click on the Configure button.