The term "domain" has more than one meaning. An Internet Domain such as ubuntuforums.org is different from a MSHOME domain. The MSHOME domain is really a workgroup and it is only needed for browsing Windows type networks (Samba).
If you want all the hosts to be in the same browsing domain (workgroup), then do like you started to do and edit the /etc/samba/smb.conf as so:
You may have been a little to quick on the trigger for Samba to recognize the addition to the workgroup. There is a routine for updating who and what is in the workgroup (Browse Master). This usually takes about 15 minutes at first. I have seen it on my network when I make changes or a user with shares first comes online.
# Workgroup/NT-domain name your Samba server will part of
workgroup = MSHOME
If you made your shares via Gnome/Nautilus you may have to remove the sharing and after a bit add them again. This sounds like your problem here:
DBus error org.freedesktop.DBus.Error.InvalidArgs: Mountpoint Already registered