The issue started appearing after upgrading the tortoise SVN to a new version. Each time the working copy is updated, we got an error saying that "Access denied on Y:/xxx/.svn/tmp/entries".
We definetly knew that it is not an SVN issue, but could be SAMBA.
After some research on Google it turned out to neither SVN nor SAMBA, but a special case where UNIX file ownership prevents changing file permissions, and DOS semantics prevent deletion of a read only file.
Luckly we found the following work around from tortoisesvn.tigris.org
After upgrading to TortoiseSVN 1.5.x or later, you get a lot of "Access denied" errors for most of the Subversion commands if your working copy is stored on a SAMBA share.
Some users reported that the problem went away after they upgraded SAMBA to the latest version. If that does not help or you can't upgrade, allow readonly files to be deleted in the SAMBA config file:[global]For older versions, try:
delete readonly = yes[global]
create mask = 0644
force create mode = 0600
security mask = 0555
force security mode = 0600