Accessing server from another domain

I have hit a glitch. Under NT4 I was able to map to another domain and server as another user without any porblems.
But under win2k Im unable to do that. I ype in \\server\share$, in different user diaolg box, I provide – domain\user & password.
Comes up “the network…path not found”
Is this a bug or is there a workaround

Thanks