I am so sorry that I made mistakes 
in permission strings and - worse - in configuration.
This problem is of importance for us
as the first Linux inroad into company... must be a successs...
Following are detailed instructions how to reproduce 
the error (?).
--------
Prologue
--------
Share configuration
[samba-test]
   comment = Samba test share
   path = /export/samba-test
   writable = yes
   valid users = @nss
   create mask = 0664
   directory mask = 0775
   inherit permissions = yes
Files on UNIX
bash-2.04$ cd /export/samba-test/
bash-2.04$ ls -la
total 20
drwxrwsr-x    2 root     nss          4096 Feb 16 17:17 .
drwxr-xr-x    5 root     root         4096 Feb 16 15:28 ..
-rw-rw-r--    1 mcader   nss         10752 Aug  1  1997 file.doc
------------------------------------------------
Step 1. Domain user mapped to rmichals:nss opens 
        and modifies file file.doc
        in Word 2000 under Windows 95.
------------------------------------------------
Files on UNIX
-rw-rw-r--    1 mcader   nss         10752 Aug  1  1997 file.doc
-rwxrw-r--    1 rmichals nss           162 Feb 16 17:21 ~$file.doc
----------------------------------------
Step 2. User tries to save modified file
----------------------------------------
Word displays OK-button dialog that it cannot save file 
because of insufficient permissions.
Files on Unix
-rw-rw-r--    1 mcader   nss         19456 Feb 16 17:27 file.doc
-rwxrw-r--    1 rmichals nss           162 Feb 16 17:28 ~$file.doc
-rw-rw-r--    1 rmichals nss         10752 Aug  1  1997 ~WRL0812.tmp
The user clicks OK.
Word diplays Yes-No-buttons dialog asking whether
to retry the save.
The user clicks No. 
The document remains open in Word.
--------------------------------------
Step 3. User closes document believing 
        only last changes will be lost
--------------------------------------
The user chooses Close button of the MDI child window
containing document.
Word displays Yes-No-Cancel-buttons dialog asking whether
to save changes.
The user clicks No.
Word closes the document.
Files on UNIX
drwxrwsr-x    2 root     nss          4096 Feb 16 17:31 .
drwxr-xr-x    5 root     root         4096 Feb 16 15:28 ..
-rw-rw-r--    1 rmichals nss         10752 Aug  1  1997 ~WRL0812.tmp
---------
Epilogue
---------
The original document is lost.
> -----Original Message-----
> From: "Michalski, Rafa?" [mailto:RMichalski@eragsm.pl]
> Sent: Friday, February 16, 2001 4:27 PM
> To: 'samba@lists.samba.org'
> Subject: MS Word files disappearing
> 
> 
> Hello All
> 
> Let me report some disastrous behavior of the daemon.
> Under several circumstances, W9x-accessed MS Word files can disappear
> from the Samba share without warning.
> 
> Our share has Unix group named nss as its valid users.
> When a domain user mapping to Unix user rafal:nss 
> and working under W95 opens file say file.doc with Unix permissions
> -rw-rw---- owned by marcin:nss, 
> Word 2000 creates temporary file ~file.doc with permissions -rwxrw----
> rafal:nss
> (archive bit is set) on the share.
> User makes some changes to the document, then tries to save.
> Gets Retry/Cancel dialog that states Word could not save the document.
> At this moment, another temporary file with extension .tmp 
> permissions -rwxrw-r-- rafal:nss
> can be observed on the share.
> The user cancels dialog, document still opened in Word.
> Tries to close the document,
> Word claims changes not saved, but assuming
> changes unimportant, the user decides to close anyway.
> Now also the original document file.doc DISAPPEARS FROM SHARE.
> 
> We did not observe this phenomenon when accessing documents 
> from WinNT.
> Also, setting archive bit on the original file file.doc helps 
> avoid the
> problem.
> 
> Our share is configured as follows.
> Let me signal that this create mask/security mask combo fails 
> to prevent
> modifying archive bit from Windows NT - why?
> 
> [nss]
>    comment = DNO/CIT/NSS common files
>    path = /export/nss
>    writable = yes
>    valid users = @nss
>    create mask = 0764
>    security mask = 0677
>    directory mask = 0775
>    inherit permissions = yes