I have the following configuration at home:

* Linux box (Debian 4.0): Samba Server
* Windows box (Windows XP SP3): Samba Client

On the linux box I have a file that is read-only:

  -r--r--r-- 1 apache servergroup 37 2008-09-26 16:48 dir-props

The directory that contains this file has the following rights:

  drwxr-xr-x 2 apache servergroup 4096 2008-09-26 17:09 .svn

This directory is accessable through a Samba share. The Samba configuration is:

  [global]
  netbios name = deepthought
  server string = Samba Server
  workgroup = Maya Group
  security = user
  encrypt passwords = yes
  smb passwd file = /srv/config/samba/smbpasswd
  guest ok = yes
  null passwords = no
  browsable = yes
  browse list = yes

  [server]
  path = /srv
  create mask = 0644
  directory mask = 0755
  valid users = manski
  force user = apache
  read only = no
  store dos attributes = no
  map read only = yes

The problem now is that I can't move/rename this file (dir-props) with the Windows API function "MoveFileEx()" through the Samba client as the file is read-only. I get an "ERROR_ACCESS_DENIED" (Code 5).

When I, however, try to do the same thing on a "native" share (i.e. from another Windows XP box) everything is fine (i.e. no error and the file is renamed afterwards).

So, I think you should change this behaviour to fit the one of "native" Windows shares. An example where this method is used is a Subversion client that tries to do a commit on a Samba share (which doesn't work).

To test this behaviour you may use the following C (maybe C++) code:

  #include <Stdio.h>
  #include <Tchar.h>
  #include <Windows.h>

  TCHAR* from_file = "Z:\\test.txt";
  TCHAR* to_file = "Z:\\test2.txt";

  int _tmain(int argc, _TCHAR* argv[])
  {
    printf("%s\n", from_file);
    if (MoveFileEx(from_file, to_file, MOVEFILE_REPLACE_EXISTING | MOVEFILE_COPY_ALLOWED)) 
    {
      printf("Good");
    } 
    else 
    {
      printf("Error: %d", GetLastError());
    }

    return 0;
  }

I hope this helps.