Sorry if this is a stupid question, but did you substitute your actual OD Group name in place of 'yourGroupName' in the command?
If so, run the following command:
dseditgroup -o read -n /Local/Default admin
You should see your local users that are in the admin group, but you should also see an entry under dsAttrTypeStandard:NestedGroups. That ID should match the GeneratedUID of your group. (You can check this in Workgroup Manager with the Inspector).
If there is nothing there, the group was never added properly.
Good luck, and let me know how you make out.
Message was edited by: Matt Ramsay