Well, Vista RC2 was released a few weeks ago, as was XBMC 2. XBMC 2 came out just after Vista RC1 was released and unfortunately the samba implementation in Vista wasn't compatible with XBMC, which as anyone who streams media from their PC using XBMC will tell you, isn't very good news.

However I did figure out a work-around until the XBMC dev team and / or samba is updated to support the new smb3 protocols. Now, unfortunately this work-around involves a little bit of work and… erm, oh yeah, and a spare box / server. If you already have a *nix server set up somewhere in your home network then you're laughing. Basically all it is, is using the *nix server as a relay. We want to run media from a Vista PC, ok, but there's no way to do that direct at the moment. So we connect the nix server to the Vista smb share and then in turn create a share on the nix server which is routed to the smb share on the Vista pc. This is possible because the latest version of smb on nix is capable of negotiating just fine with the NTLMv2 authentication of Vista. All we really need to do is configure fstab and a little credentials script then mount -a it.

So… create the share on Vista, called, say, 'PICTURES'. We want to

mkdir /home/USER/samba

then

touch /home/USER/sambacred

and then edit to populate with the following credentials:

# $HOME/sambacred
username = shareusername
password = sharepassword
domain   = WORKGROUPorDOMAIN

Then we need to add the following line to /etc/fstab

//HOSTNAME/PICTURES /home/USER/samba smbfs credentials=/home/USER/sambacred,uid=USER,gid=USERGROUP,dmask=700,fmask=700 0       0

Where "USER" is the name of the UNIX user and HOSTNAME is the name of the Vista hostname.

Once that's added to the end of fstab save and then do

mount -a
ls /home/USER/samba

and you should be listed all the files being shared on the Vista box.
Now just set up a samba share on the nix box pointing at the /home/USER/samba directory and configure XBMC to read from that samba share rather than trying (and failing) to read from the Vista box direct.

I know it's not a perfect solution, but editing the XBMC samba code and recompiling it with the XDK or arsing about in a RC operating system isn't really worth it, especially since it'll only be a short wait (hopefully) before the issue is addressed.

Oh yeah, and if you don't have the spare hardware for a relay server, you could always consider installing a virtual machine on your Vista PC (not recommended) or on another PC on the network which can be configured to act as the go between. Disregarding the doubling of network traffic it's not a big price to pay if you use it everyday. Muauhahahah! The beauty of having a gigabit network

Trying to configure access to a linux share from Vista however is a crazy hit-and-miss process. It'll first say the server isn't there, then it'll say there's a network error, then comes the authentication that fails no-matter-what, then there's a significant number of repeats… and then hey prestoo! Access. Ahh, gotta love beta software :/