I sent you a PM with my smb.conf file. Samba version is 3.0.10. And to clarify, I am running the Windows Media Connect 2.0 on an XP Pro SP2 box that is joined to the samba domain. I ran the Media Connect control panel and told it to share out \\central\media\music to everyone. The XP box then said it was scanning the folder for files for a while (I have a lot of music). This was indicated on the Settings part of the WMC screen, in the Folder Sharing area. Once it finished, I went to the music part of the dashboard, selected computer, and it found my notebook. It then let me select music to play back, and just worked.

I haven't done anything with a "NETWORK" user on my samba install. As far as I can tell, WMC on my PC is connecting to the share using my credentials, as my samba logs just show normal connects to the share, similar to when I map a drive M: to \\central\media.