Comment 5 for bug 1055075

I get the same issue. According to this:
https://wiki.samba.org/index.php/Samba4/Releases/4.0.0beta2
"smbd" is now the default, but "ntvfs" can be used.

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=694697
There was a similar bug reported here (guess this is what this package is based on?) Doesn't look like the change mentioned to make --use-ntvfs default has taken place yet, although specifying "--use-ntvfs" didn't work for me.