samba - Apr 2010 - samba 3.5.1 problem with Excel

Hello,

here's my problem :
OS: Centos 5.4 / samba: 3.5.1 (rpm from http://ftp.sernet.de )

When I try to save a document with excel to a samba share, i've got an
"inaccessible file"  error message, but the file is well saved.
When I try to export an .xls file to .csv, same problem, and the file is
not good (size = 0 k)
( No trace in logs )

With Open Office, no problem .
With MS Word, no problem .
No problem when I copy / paste a csv file from local computer to samba
share .

have someone got an idea ? what kind of information would be necessary ?
thanks for your help.

Yves

smb.conf:

[global]
        unix charset = ISO8859-15
        display charset = ISO8859-15
        workgroup = xxx
        netbios name = xxx
        server string = SERVEUR BUREAUTIQUE
        interfaces = 10.10.xxx.xxx/16, 127.0.0.1/8
        bind interfaces only = Yes
        security = DOMAIN
        client schannel = No
        server schannel = No
        passdb backend = smbpasswd
        guest account = ipconly
        pam password change = Yes
        passwd program = /usr/bin/passwd
        username map = /etc/samba/smbusers
        log file = /var/log/samba/%m.log
        smb ports = 139 445
        large readwrite = No
        name resolve order = wins lmhosts host bcast
        max wins ttl = 1000
        min wins ttl = 300
        time server = Yes
        socket options = SO_SNDBUF=2920
        printcap name = /etc/printcap
        logon script = %U.bat
        logon path = d:\Profiles_DIOSCURES\%U
        logon drive = j:
        domain logons = Yes
        os level = 99
        preferred master = Yes
        domain master = Yes
        dns proxy = No
        wins support = Yes
        ldap ssl = no
        socket address = 10.10.xxx.xxx
        valid users = root, ipconly, +itm, +burutil
        hosts allow = 10.10., 127.0.0.1
        strict allocate = Yes
        case sensitive = Yes
        map hidden = Yes
        browseable = No
        strict locking = No

and shares ...