[Samba] problem with setting times or rsync? ... smb share on ubuntu

[cedentary]

I have shared a directory from the server using the 'shares-admin'
program -- it is read/write

but I get problems in addressing files on the client - for instance:

if i issue the command 'touch testfile' on the directory I get touch:
setting times of `testfile': Permission denied

If i try to untar an archive (tar -xvf) I get multiple messages
(sample):

Cannot utime: Operation not permitted
bdeditor.css
tar: bdeditor.css: Cannot utime: Operation not permitted
BdEditor-mined.js
tar: BdEditor-mined.js: Cannot utime: Operation not permitted
bgmusic.js
tar: bgmusic.js: Cannot utime: Operation not permitted
blank.html

the last (relevant) line of my fstab file on the client machine looks
like this :

//username-desktop/keep /home/username/keep smbfs rw 0 0

I also am only allowed to save files *some of the time* and not to use cp -
partly works

Can anyone advise me as to what is the problem -- something to do with
rsync yes?