[Samba] Replacing a file turns off group and world read permissions

[Roger Lainson]

My problem is that when I *replace* a file on a share, the file 
permissions get changed from 0777 to 0733. I'm running  Samba 3.32 on 
Ubuntu Server 9.04 with both Ubuntu and Windows clients as guests. For 
some common shares I have create mask = 777 and force create mode = 777.

This works fine for creating files, but when I replace a file on this 
share by certain methods on an Ubuntu client, the permissions get set to 
0733, so the file is then unreadable (and undelete-able) by a guest. The 
problematical methods are simply dragging a repeat of the same file into 
Nautilus file browser, or performing a repeat save as from Evince 
DocViewer (which means it's a particular nuisance with PDF files). As 
far as I can see there's no problem with saving from other Ubuntu apps, 
or with Windows clients, or with Ubuntu clients on other shares which 
are not guest-accessible.

The section of smb.conf for the share is:

[SDRFiles]
    writeable = yes
    path = /var/sdr/SDRFiles
    write list = sdr
    force directory mode = 0777
    force group = sdr
    force create mode = 0777
    force user = sdr
    comment = SDR Files on server3
    guest only = yes
    public = yes
    create mode = 0777
    directory mode = 0777

Be glad of any suggestions. Thanks, Roger