Samba error "The request is not supported"

I was trying to access a Samba v3.0.20 from a Windows 2003 server, but got only error messages without much explanation.
Eg.
C:\>net use \\server3
System error 67 has occurred.

C:\>net view
Server Name            Remark

-------------------------------------------------------------------------------
\\SERVER1
\\SERVER2
\\SERVER3              server3 server (Samba, Ubuntu)
The command completed successfully.

C:\>net view \\SERVER3
System error 50 has occurred.

The request is not supported.

I've found the solution here. It says that a possible fix is if you change the security = server to security = domain. It worked for me. Now I only have to get access permissions right, because at the moment I can only read the shares. Smile