I think that you need to re-examine whether share-mode security is what you actually need for this problem. Share mode security means that a password is used to authenticate to a share, not a username/password combination.
If you want to allow multiple users (logging in as themselves) access to modify the files then you need to use user level security.
If you want to allow anybody that knows the magic password to see the share, then share mode security is right for you.
See the Samba Documentation for more information on share level security.
This might help. I do something similar, but only one share is open to the group's users. Other shares are read-only except for a single maintainer user. The [global] section of my smb.conf is almost identical to yours, except I don't use the force create/directory mode directives (in my case, they'd interfere with the other shares).
Here's the share definition:
[shared stuff]
comment = blah, blah, etc
path = /path/to/share
write list = @sambagroup
force group = +sambagroup
read only = yes
directory mask = 0775
create mask = 0664
guest ok = yes
invalid users = root
case sensitive = True
default case = lower
preserve case = yes
short preserve case = yes
The important stuff here are these:
read only = yes
-- by default, read only.
guest ok = yes
-- guests can browse.
write list = @sambagroup
-- Authenticated members of sambagroup can write.
force group = +sambagroup
-- The + means that the force only applies to existing members of sambagroup. They're already the only ones who can write. I think, without the +, guest is given sambagroup credentials, which is not wanted (particularly with the write list directive above).
directory mask = 0775
create mask = 0664
These do exactly what you want yours to do: "drwxrwxr-x" on directories, "rwxrwxr-x" on files, and newly created files are owned by the user and sambagroup. The maintainers of the other shares get the same permissions as everyone else when working in shared stuff, and permissions & groups are normal when they work in the other shares.
My smb.conf has been working with only minor tweaks through several different versions of Samba, and currently is used with Samba 3.2.5. I never had it running on Ubuntu 8.04, but it ran on Ubuntu 7.04 for a long time before getting migrated to a recent Debian Lenny install.
Best Answer
At a guess, mainly because you have this: 'map to guest = Bad User', you haven't created any Samba users. Try reading this: https://wiki.samba.org/index.php/Setting_up_Samba_as_a_Standalone_Server
You don't actually need that line because you have 'map to guest = no' set on both shares (and you don't actually need them, they are default settings).