I run a small lab of macs - all 10.6.8 including server.
Have several issues at the moment:
1) one mac won't join the appropriate computer group. One tell tale sign is the Logon message - for any computers in the group, it says "welcome to the lab". For the guest computer record it says "guest computer" so I know if computers are not assigned to a group.
I have removed the record via WGM, rejoined and binded, readded the computer record to the group and it still shows the "guest" login message. Network users can login, however.
2) I tried resetting MCX cached settings when logging in as an admin user, per http://support.apple.com/kb/HT3540, and while it does show the workgroup picker, it does not show the option to disable or refresh management settings. I tried this on any system - even ones that are properly in groups, using a network administrator account.