The Non-Ideal Solution
After reading a lot of hints, lowering the required client security on the Windows and making the OS X machine the master browser works reliably for me. However, this solution is less than ideal, as it requires reconfiguring the Mac and every Win 7 computer.
Changes to Windows 7:
- change the security policy. Using secpol.msc, go to local security, security options and find "Network security:
Minimum session security for NTLM-SSP based..." both for client and server.
(sorry, may be different, I have a German install).
- uncheck "NTLMv2 session security required"
- leave "128 encryption required" checked.
128 bit encryption works with Snow Leopard. Unchecking it is required for some older versions of OS X.
Changes to OS X Snow Leopard:
- edit /private/etc/smb.conf
- locate "os level = 2" and change to "os level = 99" which makes this samba always win
- locate "domain master = no" on next line and change to "domain master = yes"
Starting the new configuration:
- shut down your OS X and disconnect or shut down all your Windows clients.
- restart OS X. This way, OS X will become the master browser for samba.
- restart or reconnect your Windows clients.
The Very Simple Solution
By using OS X Server (properly configured), browsing will "just work", without the need to reconfigure anything else.
- Get OS X server.
- Configure SMB as Standalone Server
- enable Workgroup Master Browser
- enable Domain Master Browser
- enable WINS server
- under Access, allow NTLMv2 & Kerberos, NTLM, LAN Manager (according to what your minimum security should be)
This may be more than necessary, but it made the situation unambigous.
The problem is circumvented. It is not a principal problem of OS X Server, which uses the same Samba build as OS X client. It works reliable with the server solution. Since there is rather little interest in this topic, I will not further investigate, sorry.
About the server cost: It is quite pricey. If you happen to be registered as an Apple Developer, then you can run an evaluation copy of OS X server.