It might be due to windows 2000 encrypted passwords?
Try temporarily disabling all passwords and see if it works.
I have Samba 2.0.7 here as well, but never used it with windows 2000.
Look at some of the info on the AmigaSamba page:
http://www.birrabrothers.com/tiger/data/samba/download/index.htmOr ask on the AmigaSamba mailing list for more info.