I had this issue as well while trying to use "System -> Administration -> Services" with a user/member of the 'admin' group, using VNC and LTSP clients.
This seems to be a default Ubuntu polkit policy issue (for many things, it seems Ubuntu wants you to be on the actual system console and not logged in remotely via any means)... I don't understand this as it would be trivial to trick PolKit into thinking you're logged in locally even if you're not.
I had this issue as well while trying to use "System -> Administration -> Services" with a user/member of the 'admin' group, using VNC and LTSP clients.
Please see comment #14 at http:// ubuntuforums. org/showthread. php?p=8001955# post8001955 for my workaround.
This seems to be a default Ubuntu polkit policy issue (for many things, it seems Ubuntu wants you to be on the actual system console and not logged in remotely via any means)... I don't understand this as it would be trivial to trick PolKit into thinking you're logged in locally even if you're not.