Is it a cups printer, a lpd printer? In the /etc/smb.conf [printer] section, does it say "guest ok = yes"? If not, don't alter it there, you have to do it with the SME template system.
I don't really think, it is a SME problem rather than a Windows problem. Are the workstations connected to a domain? Is there a domain policy in effect wich prevents installing printers?