[Samba] Can not clear Read-only attribute

[tom m.]

Using 'security=share' or 'security=user', via Windows right-click any Samba
exported file and set the Read-only attribute.  This works, but now can not
clear the Read-only attribute, Windows reports simply "Access is denied".
 
This happens with 3.3.0 and 3.3.1, but NOT 3.2.3.

Setting 'force user = root' does not help.