I'm trying to svn co to a directory on Ubuntu, shared via samba, to OS X, but I get the following error (in OS X).

svn: In directory 'site/product/tests'
svn: Can't open file 'site/product/tests/.svn/tmp/text-base/._base.py.svn-base': No such file or directory

My smb.conf file includes the following changes:

unix extensions = no
browseable = yes
public = yes
writable = yes
delete readonly =  yes
create mask = 0775
directory mask = 0775
valid users = %S
read only = no

The checkout works fine locally (on the Ubuntu machine).

What am I missing?

More detail:

Later inspection showed that the svn error couldn't find the file with 3, then 2 underscores:

.___init__.py.svn-base

Whereas listing the directory in OS X showed 2, then 2 underscores:

__init__.py.svn-base

And listing the same directory in a successful checkout on Ubuntu shows nothing (because it's a temporary directory?)

I've tried the mangled = no setting in share settings, to no effect.