Hi jonno232,
I guess I'm a bit confused about exactly what you're trying to accomplish here. Do you want the Mac to authenticate to the Windows domain, using Windows accounts? Or do you just want to be able to mount a shared volume on the W2K3 machine? Exactly how are you trying to "connect"? Please describe more of what your intentions are and how you bound the Mac to the domain, and I'll have a better idea of how to troubleshoot.