Comment 1 for bug 1388524

Hi,
Thanks for taking time to report this!
This is a known bug, and is related to pkexec.

The current workaround would be to manually run this:
/usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1

or to add it to the autostart!

Since this is still in the Alpha stage we will be implementing a permenant fix to this issue.
There are, perhaps, more elegant ways of doing this rather than adding it to autostart :)

Thanks again, and let us know if this does indeed fix the issue!