It works for me. However i am not sure how.

))
My Nas server has both NFS and UPNP protocols enabled.
From XBMC I added from NFS and UPNP (File Systems/Add sources/)my shared movide folder form the NAS server.
So in my "Files" i have two folders, one for NFS share and one for UPNP share.
from XBMC/Video/Files
======================
When I try to see movie from NFS shared folder, it does not work. The screen stay black. However when I browse through my movie i can see the front cover (picture with DVD) of each movie.
When I try to see movie from UPNP shared folder, it works!!! But i do not see any front cover.
From XBMC/Video/Movies
=====================
The screen stay black. However when I browse through my movie i can see the front cover (picture with DVD) of each movie, IDMB score, etc.
It looks like it uses the NFS.
I look in sources.xml (Z:\.xbmc\userdata). I succed to access it by connecting to HDD as shared folder (Z:\.xbmc\userdata) not ftp.
See below an extract:
- <video>
<default pathversion="1" />
- <source>
<name>movies</name>
<path pathversion="1">nfs://192.168.1.211/shares/Media/movies/</path>
<path pathversion="1">nfs://192.168.1.211/shares/Media/movies_14/</path>
<path pathversion="1">nfs://192.168.1.211/shares/Media/movies_pack/</path>
<allowsharing>true</allowsharing>
</source>
- <source>
<name>LaCie-2big-NAS</name>
<path pathversion="1">upnp://55076f6e-6b79-4d65-6478-00d04b932715/0%243%2433%2484074/</path>
<path pathversion="1">upnp://55076f6e-6b79-4d65-6478-00d04b932715/0%243%2433%2482697/</path>
<path pathversion="1">upnp://55076f6e-6b79-4d65-6478-00d04b932715/0%243%2433%2470321/</path>
<allowsharing>true</allowsharing>
</source>
</video>
Hope it helps!