Ad Rights For Share?

I'm able to share a folder on my Suse 10.1 box, but it only works if I allow everyone access to it. I want to setup the share with rights for users on a Windows 2003 domain. If I access the share rights for that folder under Konqueror it allows me to open the Users tab. From here I've tried to change the "All Unspecified Users" to reject and then choose Add User... to add DOMAIN\username with admin rights to the share.
After I save the settings and try to map from a Windows XP box it asks for a username and password, but it won't take my credentials.
Any ideas?

Have you tried with smbpasswd ?