First, Root canot connect to Cifs Share, over windows station.
seconf, no the qtree isnt necessary to made a share
third, for windows authentification, correctly, you must have an NTFS security on your Volume or Qtree
and last one, Have you correctly do the CIFS setup ? And at this time the controler may ask to you to create an CIFS loacl administrator, righy ?
Could you send us the result of : cofs domaininfo