password behaviors, samba v3 versus v2

Two identically configured samba's handle password requirements
differently. Why? Did samba 3 introduce some behavior difference over
samba 2?

The 2 identical samba configurations:
The smb.conf's are 6 lines long and identical except for differing
netbios names. The smbpasswd's are identical, and are empty (zero
bytes in size). However machine #1 runs samba 2.2.5 under RedHat8
while machine #2 runs samba 3.0.3 under Fedora Core 2.

The 2 different password behaviors:
I view the 2 samba boxes from "Network Places" in a Windows box.
Viewing machine #2, I get a dialog box challenging for a user/password
combination. With machine #1 there's no such challenge and any shared
resources are immediately shown. Machine #2 will reveal shared
resources when I provide a correct user/pass combo per /etc/passwd.


Any ideas why the password behaviors differ?