just wondering, but do you have an account for the user logged on to the win2k machine set in the linux machine? If you don't, use the smbpasswd program (located in /usr/local/samba/bin) to re-enter username/password or just to enter a new user. While in the samba/bin directory, type the following to change for username (in this example):
./smbpasswd -a username
The first time a user is added, the program will output an error saying that the encrypted password database does not exist. Don't worry, it will then create the database for you and you should have access.