Browsing (Ubuntu) Samba shares, logon prompt doesn't authenticate

view story

http://serverfault.com – Setup Have an Ubuntu server here with several Samba shares for Windows machines. Have multiple Windows machines which authenticate with samba to group shares and one public share. All working perfectly and have been for many years. Recently my Manager changed a setting in smb.conf to get a Mac working, I believe it was the security = setting. It now reads security = user. The shares have valid users = set. We have a public facing Windows XP PC which is allowed access to the Public share, but when attempting to access the group shares users should be prompted to authenticate. The local user (HowTos)