what I mean by exporting is: do you make your linux filesystem available to remote machines using smb?
so are you trying to use windows to connect to a linux filesystem? i believe that samba assigns its own permissions, so if you chmod a file the settings won't be necessarily be reflected in samba (i could be wrong tho).
I think what you have to do is modify your current config. either through the samba web-based config or by hand.
check out the howto at:
it is fairly old but probably still relevant.
Or if you are trying to access a windows filesystem from linux, then check the settings on the windows box and make sure you are mounting the filesystem with an appropriate user, ie:
mount -t smbfs -o username=yourusername ....